Emerald Lake Hills or Emerald Hills is a census-designated place and neighborhood in unincorporated San Mateo County, in the state of California, USA. Situated among oak-studded hills between Woodside, Redwood City, and San Carlos roughly bounded by Edgewood Road, Alameda de las Pulgas, Farm Hill Boulevard, and Interstate 280. The population was 4,278 at the 2010 census and the per-capita income was $68,966,^[2] making it the 22nd wealthiest place in California and the 82nd wealthiest place (with a population over 1,000) in the United States

Emerald Lake Hills was originally conceived as a resort community for city-weary San Franciscans during World War I. Emerald Lake Hills actually consists of two large subdivisions created around 1920: Emerald Lake (even though there are two lakes) and Emerald Hills. Residents refer to the area by either Emerald Hills or by Emerald Lake Hills. The name Emerald Hills is now more commonly adopted due to mailing designation rules, as the U.S. Post Office would allow only a two-word name.

~  Wiki