New Madrid city, seat (1821) of New Madrid county, southeast Missouri, U.S., on the Mississippi River. It originated as an Indian trading post about 1783. The town was initiated in 1789 by an American Revolutionary War veteran, George Morgan, who had received a land grant from Spain, but it did not begin to flourish in farming and trade until after the purchase of the Territory of Louisiana by the United States in 1803. New Madrid's growth was slowed by violent earthquakes in 1811-12, as well as floods and shifting of the river's course, which caused several removals of the city to different sites. The town was the site of an American Civil War battle in 1862. New Madrid's economic mainstay is diversified agriculture (cotton, soybeans, corn [maize], grain sorghum, and livestock). Aluminum ingots, electrical conductors, and clothing are manufactured there, and there is some lumbering. The Lilbourn site, a fortified prehistoric Indian ceremonial centre, is 6 miles (10 km) west.