San Mateo County was formed in 1856 upon the division of San Francisco County, one of the state's 18 original counties established at California statehood in 1850. Until 1856, San Francisco’s city limits extended west to Divisadero Street and Castro Street, and south to 20th Street. In 1856, it was divided. A straight line was drawn across the tip of the San Francisco Peninsula just north of the San Bruno Mountains. Everything south of the line became the new San Mateo County while everything north of the line became consolidated San Francisco County. In 1868 San Mateo County annexed part of northern Santa Cruz counties with the towns of Pescadero and Pigeon Point.