Greenfield is a city in Monterey County, California, United States. Formerly Clarke Colony, it lies in the Salinas Valley, 33 miles southeast of Salinas, at an elevation of 289 feet. As of the 2020 census, the population was 18,937, up from 16,330 in the 2010 census. Its most well-known public event is the annual Harvest Festival. Greenfield is a member of the Association of Monterey Bay Area Governments.