How many California counties were there at the state's admission to the union?
25. Butte, Calaveras, Colusa,
Contra Costa, El Dorado, Los Angeles, Marin, Mariposa, Mendocino,
Monterey, Napa, Sacramento, San Diego, San Francisco, San Joaquin, Santa
Barbara, Santa Cruz, Shasta, Solano, Sonoma, Sutter, Trinity, Tuolumne,
Yolo, Yuba.