West Bay Sanitary District is a Special Sanitary District in San Mateo County, created under Chapter 161 of the Sanitary District Act of 1891 and established sanitary authorities from San Francisquito Creek to Atherton Ave. The District now serves Menlo Park, Atherton, Portola Valley, East Palo Alto, Woodside, Redwood City and Unincorporated San Mateo and Santa Clara Counties.