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- September 9, 1850
- Fall 1850
First State census: Contra Costa County---722; Santa Clara County---3,502
- May 4, 1852
Act to incorporate the City of Oakland.
- March 10, 1853
Petition to create Alameda County, from parts of Contra Costa and Santa Clara counties.
- March 26, 1853
Act of Incorporation of Alameda County.
- April 6, 1853
Act of Incorporation signed by Governor John Bigler.
- June 6, 1853
County is divided into judicial townships for the first time.
- April 4, 1854
Post office in San Lorenzo established. Albert E Crane is the first postmaster.
- April 19, 1854
Town of Alameda incorporates.
Town of San Leandro was founded of the sole, specific purpose of housing the seat of Alameda County.
- January 7, 1856
Coal mining begins in Corral Hollow (later Tesla).
- February 6, 1856
County seat moves to San Leandro.
- August 16, 1856
Gazette, first San Leandro newspaper, begins publication.