The United States acquired the area of California from Mexico in 1848, with generally the same boundary as the present state. The area of California was never organized as a territory, but was administered from 1848 to statehood by a federal military authority. California was admitted to the Union on September 9, 1850, as the 31^st state.

Census data for California are available beginning with the 1850 census; however, the data for 1850 are incomplete because the questionnaires from Contra Costa and Santa Clara Counties were lost and those for San Francisco County were destroyed by fire. Some missing 1850 data have been supplanted by information obtained from a state census in 1852.

Data for the legally established state of California are available beginning with the 1850 census.

AMERICAN INDIAN AREAS

California has 108 federally recognized American Indian areas.  There are 104 reservations; 28 with off-reservation trust land in the state.  Two are trust lands only. The remaining two are tribal designated statistical areas (TDSAs). 

METROPOLITAN AND MICROPOLITAN STATISTICAL AREAS AND RELATED STATISTICAL AREAS

California has 26 metropolitan statistical areas, 9 micropolitan statistical areas, 4 combined statistical areas, and 4 metropolitan divisions.

COUNTIES

There are 58 counties in California.  The city and county of San Francisco have consolidated functions and is classified as a municipal government that operates primarily as a city.  All other counties are each governed by a board of supervisors. 

COUNTY SUBDIVISIONS

There are 397 county subdivisions in California. They are all census county divisions (CCDs), which are delineated for statistical purposes, have no legal function, and are not governmental units.  CCDs were first established in California for the 1960 census.  Prior to 1960, the minor civil divisions used in the census included election precincts, judicial townships, supervisor’s districts, and one American Indian reservation (in 1870).

PLACES

California has 1,523 places; 480 incorporated places and 1,043 census designated places (CDPs).  The incorporated places consist of 459 cities and 21 towns.  In California an incorporated place can legally exist only in a single county.

CENSUS TRACTS/BLOCK GROUPS/BLOCKS

California has 8,057 census tracts, 23,212 block groups, and 710,145 blocks.

CONGRESSIONAL DISTRICTS

For the 111^th Congress (January 2009-January 2011), California had 53 congressional districts.  For the 113^th Congress (January 2013-January 2015), California continues to have 53 congressional districts as a result of the reapportionment based on the 2010 Census.

SCHOOL DISTRICTS

California has 548 elementary school districts, 104 secondary school districts, and 335 unified school districts. 

STATE LEGISLATIVE DISTRICTS

There are 40 state senate districts and 80 assembly districts in California.

URBAN AREAS

California has 211 urban areas; 59 urbanized areas and 152 urban clusters.

ZIP CODE TABULATION AREAS

There are 1,769 ZIP Code tabulation areas (ZCTAs) in California.

¹  Source:  U.S. Department of Commerce, Bureau of the Census, Fourteenth Census of the United States, 1923
²  Source:  U.S. Census Bureau, recomputation for historical county level data which relied upon aggregate county level population data with an estimated county centroid resulting in a possible error of up to one mile.
³  Source:  U.S. Department of Commerce, Bureau of the Census, Centers of Population for States and Counties, 1974
⁴  Source:  U.S. Census Bureau, Geography Division, recomputation from archived national block group/enumeration area data resulting in a possible error of up to 1,000 feet.
⁵  Source:  U.S. Census Bureau, Geography Division, recomputation from archived national block group data resulting in a possible error of up to 1,000 feet.
⁶  Source:  U.S. Census Bureau, computation from national block-level data