Wentzville is a city located in western St. Charles County, Missouri, United States. As of 2010, the city had a total population of 29,020. The city's major employer is General Motors which has a full size van assembly plant located there. As the site of the county fairgrounds, Wentzville hosts the annual St. Charles County Fair, St. Louis Pirate Festival and the Greater St. Louis Renaissance Faire.
Wentzville was founded in 1855 as a depot on the Northern Missouri Railroad. It was named after Erasmus Livingston Wentz, a railroad engineer for the line. The land was obtained from William M. Allen, who laid out the town. Wentzville was not incorporated until 1872.
During the American Civil War, the city was the site of a series of skirmishes along the railroad from July 15 to July 17, 1861. Elements of the 2nd and 8th Missouri Infantry Regiments en route to Mexico, Missouri engaged Confederate guerrillas who threatened the railroad.