Chesterfield is a second-ring western suburb of St. Louis and is the largest city in west St. Louis County, Missouri, United States. As of the 2010 census the population is 47,484. Chesterfield also celebrated its 20th birthday in 2008.
Chesterfield is located at 38°39′12″N 90°33′15″W / 38.65333°N 90.55417°W / 38.65333; -90.55417 (38.653402, -90.554255) about 25 miles (40 km) west of St. Louis, Missouri. According to the United States Census Bureau, the city has a total area of 32.7 square miles (84.8 km²), of which, 31.5 square miles (81.6 km²) of it is land and 1.2 square miles (3.2 km²) of it (3.73%) is water.
Portions of Chesterfield are located in the floodplain of the Missouri River, now known as Chesterfield Valley, formerly Gumbo Flats. This area was submerged during the Great Flood of 1993; higher levees built since then have led to extensive commercial development in the valley. Chesterfield Valley is the location of Spirit of St. Louis Airport, used for corporate aviation, as well as the longest outdoor strip mall in America . The remainder of Chesterfield is located on the bluffs above the floodplain, and includes residential and retail development.