United States congressional apportionment

United States congressional apportionment is the process by which seats in the United States House of Representatives are distributed among the 50 states according to the most recent constitutionally mandated decennial census. Each state is apportioned a number of seats which approximately corresponds to its share of the aggregate population of the 50 states. However, every state is constitutionally guaranteed at least one seat.

Allocation of congressional districts in the House of Representatives after the 2010 census.

Allocation of congressional districts after the 2000 census.

Reapportionment

The 435 seats of the House grouped by state (post-2010 Census reapportionment).

While citizens of each state are given nearly equal voting power through representation in the House, the situation in the Senate is significantly different where each state gets two votes no matter how large its population may be. A Wyoming voter, therefore, has roughly 66 times more representation in the Senate than a California voter. (Citizens in DC and territories have no voting power in Congress.)

The number of seats in the House of Representatives is currently set to 435, and has been since 1913, except for a temporary increase to 437 after the admissions of Alaska and Hawaii. Though the actual reapportionment will normally occur in respect of a decennial census, the law that governs the total number of representatives and the method of apportionment to be carried into force at that time can be created prior to the census.

The decennial apportionment also determines the size of each state's representation in the U.S. Electoral College—that is, any state's number of electors equals the size of its total congressional delegation (i.e., House seat(s) plus Senate seats).

Federal law requires the Clerk of the House of Representatives to notify each state government of its entitled number of seats no later than January 25 of the year immediately following the census. After seats have been reapportioned, each state determines the boundaries of congressional districts—geographical areas within the state of approximately equal population—in a process called redistricting. Any citizen of the State can challenge the constitutionality of the redistricting in their US district court.

Because the deadline for the House Clerk to report the results does not occur until the following January, and the states need sufficient time to perform the redistricting, the decennial census does not affect the elections that are held during that same year. For example, the electoral college apportionment during 2000 presidential election was still based on the 1990 census results. Likewise, the congressional districts and the electoral college during the 2020 general elections will still be based on the 2010 census.

Constitutional texts

The subject of Congressional apportionment is addressed twice in the U.S. Constitution. Initially, the apportionment of House seats was guided by two sentences in Article I, Section 2, clause 3:

Representatives and direct Taxes shall be apportioned among the several States which may be included within this Union, according to their respective Numbers, which shall be determined by adding to the whole Number of free Persons, including those bound to Service for a Term of Years, and excluding Indians not taxed, three fifths of all other Persons. The Number of Representatives shall not exceed one for every thirty Thousand, but each State shall have at least one Representative;…

Following the end of the Civil War, the first of those provisions was superseded by Section 2 of the Fourteenth Amendment:

Representatives shall be apportioned among the several States according to their respective numbers, counting the whole number of persons in each State, excluding Indians not taxed, But when the right to vote at any election for the choice of electors for President and Vice-President of the United States, Representatives in Congress, the Executive and Judicial officers of a State, or the members of the Legislature thereof, is denied to any of the male inhabitants of such State, being twenty-one years of age, and citizens of the United States, or in any way abridged, except for participation in rebellion, or other crime, the basis of representation therein shall be reduced in the proportion which the number of such male citizens shall bear to the whole number of male citizens twenty-one years of age in such State.

House size

Ratio of representation in the House, 1789–1913

Years	Source	Constituents per Rep.
1789	U.S. Const.	≥30,000
1793–1803	1790 Census	34,436
1803–1813	1800 Census	34,609
1813–1823	1810 Census	36,377
1823–1833	1820 Census	42,124
1833–1843	1830 Census	49,712
1843–1853	1840 Census	71,338
1853–1863	1850 Census	93,020
1863–1873	1860 Census	122,614
1873–1883	1870 Census	130,533
1883–1893	1880 Census	151,912
1893–1903	1890 Census	173,901
1903–1913	1900 Census	193,167
1913–1923	1910 Census	210,583

The U.S. population has increased more rapidly than the membership of the House of Representatives.

The size of the U.S. House of Representatives refers to total number of congressional districts (or seats) into which the land area of the United States proper has been divided. The number of voting representatives is currently set at 435. There are an additional five delegates to the House of Representatives. They represent the District of Columbia and the territories of American Samoa, Guam, the Northern Mariana Islands, which first elected a representative in 2008, and the U.S. Virgin Islands. Puerto Rico also elects a resident commissioner every four years.

Controversy and history

Since 1789, when the Federal Government began operating under the Constitution, the number of citizens per congressional district has risen from an average of 33,000 in 1790 to almost 700,000 as of 2008. Prior to the 20th century, the number of representatives increased every decade as more states joined the union, and the population increased. In 1911, Public Law 62-5 raised the membership of the U.S. House to 433 with a provision to add one permanent seat each upon the admissions of Arizona and New Mexico as states. As provided, membership increased to 435 in 1912.

In 1921, Congress failed to reapportion the House membership as required by the United States Constitution. This failure to reapportion may have been politically motivated, as the newly elected Republican majority may have feared the effect such a reapportionment would have on their future electoral prospects. Then in 1929 Congress (Republican control of both houses of congress and the presidency) passed the Reapportionment Act of 1929 which capped the size of the House at 435 (the then current number). This cap has remained unchanged for more than eight decades. Three states – Wyoming, Vermont, and North Dakota – have populations smaller than the average for a single district.

The "ideal" number of members has been a contentious issue since the country's founding. George Washington agreed that the original representation proposed during the Constitutional Convention (one representative for every 40,000) was inadequate and supported an alteration to reduce that number to 30,000. This was the only time that Washington pronounced an opinion on any of the actual issues debated during the entire convention.

In Federalist No. 55, James Madison argued that the size of the House of Representatives has to balance the ability of the body to legislate with the need for legislators to have a relationship close enough to the people to understand their local circumstances, that such representatives' social class be low enough to sympathize with the feelings of the mass of the people, and that their power be diluted enough to limit their abuse of the public trust and interests.

"... first, that so small a number of representatives will be an unsafe depositary of the public interests; secondly, that they will not possess a proper knowledge of the local circumstances of their numerous constituents; thirdly, that they will be taken from that class of citizens which will sympathize least with the feelings of the mass of the people, and be most likely to aim at a permanent elevation of the few on the depression of the many;..."

Madison also addressed Anti-Federalist claims that the representation would be inadequate, arguing that the major inadequacies are of minimal inconvenience since these will be cured rather quickly by virtue of decennial reapportionment. He noted, however,

"I take for granted here what I shall, in answering the fourth objection, hereinafter show, that the number of representatives will be augmented from time to time in the manner provided by the Constitution. On a contrary supposition, I should admit the objection to have very great weight indeed."

Madison argued against the assumption that more is better:

"Sixty or seventy men may be more properly trusted with a given degree of power than six or seven. But it does not follow that six or seven hundred would be proportionally a better depositary. And if we carry on the supposition to six or seven thousand, the whole reasoning ought to be reversed. ... In all very numerous assemblies, of whatever character composed, passion never fails to wrest the scepter from reason."

Clemons v. Department of Commerce

Main article: Clemons v. Department of Commerce

A 2009 lawsuit, Clemons v. Department of Commerce, sought a court order for Congress to increase the size of the House's voting membership and then reapportion the seats in accordance with the population figures of the 2010 Census. The intent of the plaintiff was to rectify the disparity of congressional district population sizes among the states that result from the present method of apportionment. Upon reaching the U.S. Supreme Court in December 2010, the holdings of the lower district and appellate courts were vacated and the case remanded to the U.S. District Court from which the case originated with instructions that the district court dismiss the case for lack of jurisdiction.

Proposed expansion

The first proposed amendment to the Constitution within the Bill of Rights attempted to set a pattern for growth of the House along with the population, but has not been ratified.

Article the first... After the first enumeration required by the first article of the Constitution, there shall be one Representative for every thirty thousand, until the number shall amount to one hundred, after which the proportion shall be so regulated by Congress, that there shall be not less than one hundred Representatives, nor less than one Representative for every forty thousand persons, until the number of Representatives shall amount to two hundred; after which the proportion shall be so regulated by Congress, that there shall not be less than two hundred Representatives, nor more than one Representative for every fifty thousand persons.

The proposed Wyoming Rule calls for expanding the House until the standard Representative-to-population ratio equals that of the smallest entitled unit (currently the state of Wyoming). This proposal is primarily designed to address the fact that some House districts are currently nearly twice the size of others; for instance, there are nearly 1 million residents in Montana's single district, compared to about 570,000 in Wyoming's. See List of U.S. states by population. It should be noted that, while a larger House size will generally result in the smallest and largest districts being proportionally closer in size, this is not always the case. Therefore in some cases, the Wyoming Rule may actually result in an increase in the ratio of the sizes of the largest and smallest districts. For instance, after the 1990 Census and with a House size of 435, the largest district (Montana's At-large district) had 799,065 residents, 76% larger than the smallest district (Wyoming's At-large district with 453,588 residents). The Wyoming Rule would have given a House size of 547 in 1990. Using that size, the largest district (North Dakota's At-large district) would have had 638,800 residents, 92% larger than the smallest districts (Delaware's two districts at approximately 333,084 residents each), which is larger than the 76% figure mentioned above.

On May 21, 2001, Rep. Alcee Hastings sent a dear colleague letter pointing out that U.S. expansion of its legislature had not kept pace with other countries.

In 2007, during the 110th Congress, Representative Tom Davis introduced a bill in the House of Representatives that would add two seats to the House, one for Utah and one for the District of Columbia. It was passed by the House, but was tripped up by procedural hurdles in Senate and withdrawn from consideration. An identical bill was reintroduced during the 111th Congress. In February 2009 the Senate adopted the measure 61-37. In April 2010, however, House leaders decided to shelve the proposal.

Apportionment methods

Apart from the requirement that the number of delegates for each state is at least one, a state's number of representatives is in principle proportional to population, thus assuring reasonably consistent representation to the people regardless of the state boundaries and populations. No method of calculating a fair distribution of voting power across the various states was known until recently and five distinct apportionment methods have been used since the adoption of the Constitution, none of them producing fully proportional distribution of power among the states.

The current method, known as the method of equal proportions, has been used since the 1940 Census. The Vinton or Hamilton method, used from 1850 to 1900, was susceptible to what is known as the apportionment paradox or Alabama paradox.

In 2008, a so-called One-Person-One-Vote model was sugested by J. Toplak in Temple Law Review, which would distribute the states' power in the House of Representatives exactly 'according to their Numbers'. Under this system, however, members of the House of Representatives do not have equal voting power. Some claim that this method would be constitutional, asserting that the U.S. Constitution does not require Congressmen to have equal voting powers but does require the voters to have votes of equal weight.

The Method of Equal Proportions

Further information: Huntington–Hill method

The apportionment methodology currently used is the method of equal proportions, so called because it guarantees that no additional transfer of a seat (from one state to another) will reduce the ratio between the numbers of persons per representative in any two states. According to NationalAtlas.gov, the method of equal proportions minimizes the percentage differences in the populations of the congressional districts.

In this method, as a first step, each of the 50 states is given its one guaranteed seat in the House of Representatives, leaving 385 seats to assign.

The remaining seats are allocated one at a time, to the state with the highest priority number. Thus, the 51st seat would go to the most populous state (currently California). The priority number is determined by a formula that is mathematically computed to be the ratio of the state population to the geometric mean of the number of seats it currently holds in the assignment process, n (initially 1), and the number of seats it would hold if the seat were assigned to it, n+1.

The formula for determining the priority of a state to be apportioned the next available seat defined by the method of equal proportions is

$A_{n}={\frac {P}{\sqrt {n(n+1)}}}$

where P is the population of the state, and n is the number of seats it currently holds before the possible allocation of the next seat. An equivalent, recursive definition is

$A_{n+1}={\sqrt {\frac {n}{n+2}}}\ A_{n}$

where n is still the number of seats the state has before allocation of the next, and for n = 1, the initial A₁ is explicitly defined as

$A_{1}={\frac {P}{\sqrt {2}}}$

Consider the reapportionment following the 2010 U.S. Census: beginning with all states initially being allocated one seat, the largest value of A₁ corresponds to the largest state, California, which is allocated seat 51. After being allocated its 2nd seat, its priority value decreases to its A₂ value, which is reordered to a position back in line. The 52nd seat goes to Texas, the 2nd largest state, because its A₁ priority value is larger than the A_n of any other state. However, the 53rd seat goes back to California because its A₂ priority value is larger than the A_n of any other state. The 54th seat goes to New York because its A₁ priority value is larger than the A_n of any other state at this point. This process continues until all remaining seats are assigned. Each time a state is assigned a seat, n is incremented by 1, causing its priority value to be reduced and reordered among the states, whereupon another state normally rises to the top of the list.

The Census 2010 Ranking of Priority Values shows the order in which seats 51–435 were apportioned after the 2010 Census, with additional listings for the next five priorities. Minnesota was allocated the final (435th) seat. North Carolina, which gained the 435th seat in the 2000 census, missed its 14th seat by 15,754 residents as the 436th seat to be allocated.

Past apportionments

See also: Apportionment Bill

Note: The first apportionment was established by the Constitution based on population estimates made by the Philadelphia Convention, and was not based on any census or enumeration.

Census, Year	Effected	Size	AL	AK	AZ	AR	CA		CO	CT	DE	FL	GA		HI	ID	IL	IN	IA		KS	KY	LA	ME	MD		MA	MI	MN	MS	MO		MT	NE	NV	NH	NJ		NM	NY	NC	ND	OH		OK	OR	PA	RI	SC		SD	TN	TX	UT	VT		VA	WA	WV	WI	WY
Const.	1789	65	–	–	–	–	–		–	5	1	–	3		–	–	–	–	–		–	–	–	–	6		8	–	–	–	–		–	–	–	3	4		–	6	5	–	–		–	–	8	1	5		–	–	–	–	–		10	–	–	–	–
1st, 1790	1793	105	–	–	–	–	–		–	7	1	–	2		–	–	–	–	–		–	2	–	–	8		14	–	–	–	–		–	–	–	4	5		–	10	10	–	–		–	–	13	2	6		–	–	–	–	2		19	–	–	–	–
2nd, 1800	1803	142	–	–	–	–	–		–	7	1	–	4		–	–	–	–	–		–	6	–	–	9		17	–	–	–	–		–	–	–	5	6		–	17	12	–	1		–	–	18	2	8		–	3	–	–	4		22	–	–	–	–
3rd, 1810	1813	182	–	–	–	–	–		–	7	2	–	6		–	–	–	–	–		–	10	1	–	9		20	–	–	–	–		–	–	–	6	6		–	27	13	–	6		–	–	23	2	9		–	6	–	–	6		23	–	–	–	–
4th, 1820	1823	213	3	–	–	–	–		–	6	1	–	7		–	–	1	3	–		–	12	3	7	9		13	–	–	1	1		–	–	–	6	6		–	34	13	–	14		–	–	26	2	9		–	9	–	–	5		22	–	–	–	–
5th, 1830	1833	240	5	–	–	–	–		–	6	1	–	9		–	–	3	7	–		–	13	3	8	8		12	–	–	2	2		–	–	–	5	6		–	40	13	–	19		–	–	28	2	9		–	13	–	–	5		21	–	–	–	–
6th, 1840	1843	223	7	–	–	1	–		–	4	1	–	8		–	–	7	10	–		–	10	4	7	6		10	3	–	4	5		–	–	–	4	5		–	34	9	–	21		–	–	24	2	7		–	11	–	–	4		15	–	–	–	–
7th, 1850	1853	234	7	–	–	2	2		–	4	1	1	8		–	–	9	11	2		–	10	4	6	6		11	4	–	5	7		–	–	–	3	5		–	33	8	–	21		–	–	25	2	6		–	10	2	–	3		13	–	–	3	–
8th, 1860	1863	241	6	–	–	3	3		–	4	1	1	7		–	–	14	11	6		1	9	5	5	5		10	6	2	5	9		–	–	–	3	5		–	31	7	–	19		–	1	24	2	4		–	8	4	–	3		11	–	–	6	–
9th, 1870	1873	292	8	–	–	4	4		–	4	1	2	9		–	–	19	13	9		3	10	6	5	6		11	9	3	6	13		–	1	1	3	7		–	33	8	–	20		–	1	27	2	5		–	10	6	–	3		9	–	3	8	–
10th, 1880	1883	325	8	–	–	5	6		1	4	1	2	10		–	–	20	13	11		7	11	6	4	6		12	11	5	7	14		–	3	1	2	7		–	34	9	–	21		–	1	28	2	7		–	10	11	–	2		10	–	4	9	–
11th, 1890	1893	356	9	–	–	6	7		2	4	1	2	11		–	1	22	13	11		8	11	6	4	6		13	12	7	7	15		1	6	1	2	8		–	34	9	1	21		–	2	30	2	7		2	10	13	–	2		10	2	4	10	1
Census	Effected	Size	AL	AK	AZ	AR	CA		CO	CT	DE	FL	GA		HI	ID	IL	IN	IA		KS	KY	LA	ME	MD		MA	MI	MN	MS	MO		MT	NE	NV	NH	NJ		NM	NY	NC	ND	OH		OK	OR	PA	RI	SC		SD	TN	TX	UT	VT		VA	WA	WV	WI	WY
12th, 1900	1903	386	9	–	–	7	8		3	5	1	3	11		–	1	25	13	11		8	11	7	4	6		14	12	9	8	16		1	6	1	2	10		–	37	10	2	21		–	2	32	2	7		2	10	16	1	2		10	3	5	11	1
13th, 1910	1913	435	10	–	1	7	11		4	5	1	4	12		–	2	27	13	11		8	11	8	4	6		16	13	10	8	16		2	6	1	2	12		1	43	10	3	22		8	3	36	3	7		3	10	18	2	2		10	5	6	11	1
14th, 1920	Congress failed to pass any reapportionment act. Distribution of seats from 1913 remained in effect, despite population shifts.
15th, 1930	1933	435	9	–	1	7	20		4	6	1	5	10		–	2	27	12	9		7	9	8	3	6		15	17	9	7	13		2	5	1	2	14		1	45	11	2	24		9	3	34	2	6		2	9	21	2	1		9	6	6	10	1
16th, 1940	1943	435	9	–	2	7	23		4	6	1	6	10		–	2	26	11	8		6	9	8	3	6		14	17	9	7	13		2	4	1	2	14		2	45	12	2	23		8	4	33	2	6		2	10	21	2	1		9	6	6	10	1
17th, 1950	1953	435	9	–	2	6	30		4	6	1	8	10		–	2	25	11	8		6	8	8	3	7		14	18	9	6	11		2	4	1	2	14		2	43	12	2	23		6	4	30	2	6		2	9	22	2	1		10	7	6	10	1
18th, 1960	1963	435	8	1	3	4	38		4	6	1	12	10		2	2	24	11	7		5	7	8	2	8		12	19	8	5	10		2	3	1	2	15		2	41	11	2	24		6	4	27	2	6		2	9	23	2	1		10	7	5	10	1
19th, 1970	1973	435	7	1	4	4	43		5	6	1	15	10		2	2	24	11	6		5	7	8	2	8		12	19	8	5	10		2	3	1	2	15		2	39	11	1	23		6	4	25	2	6		2	8	24	2	1		10	7	4	9	1
20th, 1980	1983	435	7	1	5	4	45		6	6	1	19	10		2	2	22	10	6		5	7	8	2	8		11	18	8	5	9		2	3	2	2	14		3	34	11	1	21		6	5	23	2	6		1	9	27	3	1		10	8	4	9	1
21st, 1990	1993	435	7	1	6	4	52		6	6	1	23	11		2	2	20	10	5		4	6	7	2	8		10	16	8	5	9		1	3	2	2	13		3	31	12	1	19		6	5	21	2	6		1	9	30	3	1		11	9	3	9	1
22nd, 2000	2003	435	7	1	8	4	53		7	5	1	25	13		2	2	19	9	5		4	6	7	2	8		10	15	8	4	9		1	3	3	2	13		3	29	13	1	18		5	5	19	2	6		1	9	32	3	1		11	9	3	8	1
23rd, 2010	2013	435	7	1	9	4	53		7	5	1	27	14		2	2	18	9	4		4	6	6	2	8		9	14	8	4	8		1	3	4	2	12		3	27	13	1	16		5	5	18	2	7		1	9	36	4	1		11	10	3	8	1
Census, Year	Effected	Size	AL	AK	AZ	AR	CA		CO	CT	DE	FL	GA		HI	ID	IL	IN	IA		KS	KY	LA	ME	MD		MA	MI	MN	MS	MO		MT	NE	NV	NH	NJ		NM	NY	NC	ND	OH		OK	OR	PA	RI	SC		SD	TN	TX	UT	VT		VA	WA	WV	WI	WY

Changes following the 2010 census

On December 21, 2010 the U.S. Census Bureau released its official apportionment results for congressional representation. The changes were in effect for the U.S. elections in 2012.

Gain four	Gain two	Gain one	Lose one	Lose two
Texas	Florida	Arizona Georgia Nevada South Carolina Utah Washington	Illinois Iowa Louisiana Massachusetts Michigan Missouri New Jersey Pennsylvania	New York Ohio

Past increases

The size of the U.S. House has increased as follows:

1789–1800

Date	Size	Change	Citation	Comments
March 4, 1789	59	n/a	Const. Art. I, § 2, cl. 3	Seats apportioned by the Constitution
November 21, 1789	64	5		North Carolina ratified the Constitution with the seats apportioned by the Constitution
May 29, 1790	65	1		Rhode Island ratified the Constitution with the seats apportioned by the Constitution
March 4, 1791	67	2	1 Stat. 191	Vermont admitted
June 1, 1792	69	2		Kentucky admitted
March 4, 1793	105	36	Apportionment Act of 1792, 1 Stat. 253	Apportionment of the First Census
June 1, 1796	106	1	1 Stat. 492	Tennessee admitted

1801–1820

Date	Size	Change	Citation	Comments
March 1, 1803	107	1	2 Stat. 175	Ohio admitted.
March 4, 1803	142	35	2 Stat. 128	Apportionment of the Second Census.
April 30, 1812	143	1	2 Stat. 703	Louisiana admitted.
March 4, 1813	182	39	2 Stat. 669	Apportionment of the Third Census.
December 11, 1816	183	1	3 Stat. 290	Indiana admitted.
December 10, 1817	184	1	3 Stat. 349	Mississippi admitted.
December 3, 1818	185	1	3 Stat. 430	Illinois admitted.
December 14, 1819	186	1	3 Stat. 492	Alabama admitted.
March 15, 1820			3 Stat. 555	Maine admitted, 7 seats transferred from Massachusetts

1821–1840

Date	Size	Change	Citation	Comments
August 10, 1821	187	1	3 Stat. 547	Missouri admitted
March 4, 1823	213	26	3 Stat. 651	Apportionment of the Fourth Census
March 4, 1833	240	27	4 Stat. 516	Apportionment of the Fifth Census
June 15, 1836	241	1	5 Stat. 51	Arkansas admitted
January 26, 1837	242	1	5 Stat. 50	Michigan admitted

1841–1853

Date	Size	Change	Citation	Comments
March 4, 1843	223	19	5 Stat. 491	Apportionment of the Sixth Census, the only time the size of the House was reduced, except for the minor readjustment in 1963.
March 3, 1845	224	1	5 Stat. 743	Florida admitted.
December 29, 1845	226	2	5 Stat. 798	Texas annexed and admitted.
December 28, 1846	228	2	5 Stat. 743 9 Stat. 52	Iowa admitted.
May 29, 1848	230	2	9 Stat. 58 9 Stat. 235	Wisconsin admitted.
March 4, 1849	231	1	9 Stat. 235	Wisconsin given another seat.
September 9, 1850	233	2	9 Stat. 452	California admitted.
March 4, 1853			9 Stat. 432	Apportionment of the Seventh Census.
	234	1	10 Stat. 25	Additional seat apportioned to California

The 1850 Apportionment bill provided a method to be used in future reapportionments, as well as establishing the then-current 233 as the number of seats to be apportioned after future censuses. Due to census returns being incomplete in California, an additional act provided that California retain the same representation it had when admitted, until a new census could be taken. California would otherwise have lost one seat, and so the total number of seats was increased by one to 234.

1854–1880

Date	Size	Change	Citation	Comments
May 11, 1858	236	2	11 Stat. 166	Minnesota admitted.
February 14, 1859	237	1	11 Stat. 383	Oregon admitted.
January 29, 1861	238	1	11 Stat. 269	Kansas admitted
June 2, 1862	239	1	12 Stat. 411	California apportioned an extra seat
March 4, 1863	233	6	9 Stat. 432	Apportionment of the Eighth Census, in accordance with the 1850 act, which provided for an apportionment of 233 seats
	241	8	12 Stat. 353	Supplemental apportionment of 8 seats, for an overall increase of 2 seats in the 38th Congress
June 20, 1863			12 Stat. 633	West Virginia admitted, three seats transferred from Virginia
October 31, 1864	242	1	13 Stat. 32	Nevada admitted
March 1, 1867	243	1	14 Stat. 391	Nebraska admitted
March 4, 1873	283	40	17 Stat. 28	Apportionment of the Ninth Census, replacing the 1850 act
	292	9	17 Stat. 192	Supplemental apportionment added one seat each for nine states
August 1, 1876	293	1	13 Stat. 34	Colorado admitted

1881–1900

Date	Size	Change	Citation	Comments
March 4, 1883	325	32	47th Congress, ch. 20, 22 Stat. 5	Apportionment of the Tenth Census.
November 2, 1889	328	3		North Dakota and South Dakota admitted. One seat goes to the former, two to the latter.
November 8, 1889	329	1		Montana admitted.
November 11, 1889	330	1		Washington admitted.
July 3, 1890	331	1		Idaho admitted.
July 10, 1890	332	1		Wyoming admitted.
March 4, 1893	356	24	Apportionment Act of 1891	Apportionment of the Eleventh Census.
January 4, 1896	357	1		Utah admitted.

1901–present

Date	Size	Change	Citation	Comments
March 4, 1903	386	29	Apportionment Act of 1901, 31 Stat. 733	Apportionment of the Twelfth Census
November 16, 1907	391	5	Oklahoma Enabling Act	Oklahoma admitted
January 6, 1912	393	2	Apportionment Act of 1911, Sec. 2; New Mexico Enabling Act	New Mexico admitted
February 14, 1912	394	1	Apportionment Act of 1911, Sec. 2	Arizona admitted
March 4, 1913	435	41	Apportionment Act of 1911, Pub. L. 62–5, 37 Stat. 13	Apportionment of the Thirteenth Census
January 3, 1959	436	1	Alaska Statehood Act	Alaska admitted
August 21, 1959	437	1	Hawaii Admission Act	Hawaii admitted
January 3, 1963	435	2	Reapportionment Act of 1929, ch. 28, 46 Stat. 26, 2 U.S.C. § 2a	Apportionment of the Eighteenth Census Note: The Reapportionment Act of 1929 stated that the "then existing number of Representatives" would be apportioned after each census, which would have dictated an apportionment of 437 seats, but the Alaska Statehood Act and Hawaii Admission Act explicitly stated that the new seats were temporary increases

See also

• Apportionment paradox
• Article the First
• Gerrymandering
• List of U.S. states by population
• List of U.S. states by historical population (tables of state populations since 1790)
• Redistricting
• United States Congress

Notes

• Delegate counts in italics represent temporary counts assigned by Congress until the next decennial census or by the U.S. Constitution in 1789 until the first U.S. Census.
• Elections held in the year of a census use the apportionment determined by the previous census.

References

• Balinski, Michael L.; Young, H. Peyton (1982). Fair Representation: Meeting the Ideal of One Man, One Vote. New Haven, CT: Yale University Press. ISBN 0-8157-0090-3.
• Foster, Robert (1895). Commentaries on the Constitution of the United States: Historical and Judicial. Vol. 1. Boston: The Boston Book Co. pp. 329–446.
• Hamilton, Alexander; Madison, James; Jay, John (1831). The Federalist. Hallowell: Glazier, Masters & Co. ISBN 0-8239-5735-7.
• Edelman, Paul H. (2006). "Getting the Math Right: Why California Has Too Many Seats in the House of Representatives". Vanderbilt Law Review. 102 (March). Nashville: Vanderbilt University: 297.
• Kromkowski, Charles A.; Kromkowski, John A. (1991). "Why 435? A Question of Political Arithmetic" (PDF). Polity. 24 (Fall 1991): 129–145. doi:10.2307/3234988. JSTOR 3234988. Retrieved 2013-10-17. {{cite journal}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
• Agnew, Robert A. (2008). "Optimal Congressional Apportionment". American Mathematical Monthly. 115 (April). Mathematical Association of America: 297–303.

Further reading

• Stinebrickner-Kauffman, Taren (2004). "Counting Matters: Prison Inmates, Population Bases, and "One Person, One Vote"". Virginia Journal of Social Policy & the Law. 11 (Winter). Chicago: Virginia Journal of Social Policy & the Law: 229.

External links

• Congressional Apportionment by the U.S. Census Bureau
• Thirty-thousand.org
• Commentaries and More Information on Increasing U.S. House Size.