North American area code 650 is a California telephone area code which includes most of San Mateo County (except the northernmost portion) and the extreme northwestern portion of Santa Clara County including Palo Alto, Mountain View, and Los Altos.
The 650 area was created by a split from area code 415. A six month "permissive dialing" period when either area code would work began August 2, 1997. Mandatory dialing of the new area code started on January 31, 1998.
Santa Clara County - Population 1,781,642
San Mateo County - Population 718,451
Half Moon Bay
South San Francisco