Half Moon Bay is a coastal city in San Mateo County, California, United States, approximately 25 miles south of San Francisco. Its population was 11,324 as of the 2010 census. Immediately at the north of Half Moon Bay is Pillar Point Harbor and the unincorporated community of Princeton-by-the-Sea. The urban area had a population of 20,713 at the same census. Half Moon Bay is known for Mavericks, a big-wave surf location. It is called Half Moon Bay because of its crescent shape.