Saint Charles is a city in, and the county seat of, St. Charles County, Missouri, United States. The population was 65,794 at the 2010 census, making St. Charles the ninth-largest city in Missouri. Situated on the Missouri River, it is a northwestern suburb of St. Louis.
Founded circa 1769 as Les Petites Côtes, or "The Little Hills" in French, by Louis Blanchette, a French-Canadian fur trader, when the area was nominally ruled by Spain following the Seven Years' War, St. Charles is the third-oldest city in Missouri. For a time, it played a significant role in the United States' westward expansion as a river port and starting point of the Boone's Lick Road to the Boonslick.
St. Charles was settled primarily by French-speaking colonists from Canada in its early days and was considered the last "civilized" stop by the Lewis and Clark Expedition in 1804, which was exploring the western territory after the United States made the Louisiana Purchase. The city served as the first Missouri capital from 1821 to 1826, and is the site of the Saint Rose Philippine Duchesne shrine.