Father Francisco Dumetz named San Bernardino on May 20, 1810, feast day of St. Bernardino of Siena.

San Bernardino County was formed from parts of Los Angeles County in 1853. Parts of the county's territory were given to Riverside County in 1893.

The Franciscans gave the name San Bernardino to the snowcapped peak in southern California, in honor of the saint and it is from him that the county derives its name.