Vallejo is the largest city in Solano County, California, United States. It is located in the San Francisco Bay Area on the northeastern shore of San Pablo Bay. Vallejo is named for General Mariano Guadalupe Vallejo.
Vallejo has twice served as the capital of the state of California: once in 1852 and again in 1853, both periods being brief. Some of the first Europeans drawn to the Vallejo area were attracted by the sulfur springs. In the year 1902, the area was named Blue Rock Springs.