Neils Island (sometimes called Neil Island) is a former island in Sonoma County, California, close to (and formerly surrounded by wetlands of) the Petaluma River, upstream of San Pablo Bay (an embayment of San Francisco Bay). Its coordinates are 38°11′27″N 122°34′41″W / 38.19083°N 122.57806°W / 38.19083; -122.57806 (Neils Island), and the United States Geological Survey measured its elevation as 82 ft (25 m) in 1981. It appears in a 1954 USGS map of the region.