Long Island is a small island in the Sacramento–San Joaquin River Delta. It is part of Sacramento County, California. Its coordinates are 38°10′01″N 121°37′30″W / 38.16694°N 121.62500°W / 38.16694; -121.62500 (Long Island), and the United States Geological Survey measured its elevation as 7 ft (2.1 m) in 1981. It appears on 1978 USGS maps of the area.