San Jose is tied for the second oldest incorporated city in what is now the state of California. Soon after becoming an independent territory from Mexico and while applying for statehood, Sacramento incorporated first on 2/27/1850 as a city of California. Second to incorporate were three cities: San Jose, San Diego, and Benicia on 3/27/1850. California officially became the 31st state of the United States of America soon afterwards on 9/9/1850.
Sources:
1) Clyde Arbuckle’s history of San José, book by Clyde Arbuckle, 1986, page 26.
2) https://localwiki.org/sac/History , 2019.
3) https://www.parks.ca.gov/?page_id=23856 , 2019.