Huntsville is a city in the Appalachian region of northern Alabama and is the county seat of Madison County. The city also extends west into neighboring Limestone County and south into Morgan County.It was founded in 1805 and became an incorporated town in 1811. The city grew across nearby hills north of the Tennessee River, adding textile mills, then munitions factories, NASA's Marshall Space Flight Center and the United States Army Aviation and Missile Command nearby at the Redstone Arsenal. The National Trust for Historic Preservation named Huntsville to its "America's Dozen Distinctive Destinations for 2010" list.The city's population is 215,006 as of the 2020 census, making it Alabama's most populous city. Huntsville is the largest city in the five-county Huntsville-Decatur-Albertville, AL Combined Statistical Area. The Huntsville metropolitan area's population was 492,000 as of 2020, making it the second most populous metropolitan area in the state after the Birmingham metropolitan area. The Huntsville metro's population reached 462,693 by 2018.