Madison County is named in honor of James Madison, fourth President of the United States of America, and the first to visit the state of Alabama. According to the Census' 2008 estimate, the population was 319,510. Its county seat is Huntsville. Madison County covers parts of the former Decatur County.
Madison County was established on December 13, 1808 by the governor of the Mississippi territory. Madison County is recognized as the "birthplace" of Alabama, which was founded there on December 14, 1819. For much of the county's history, the economy revolved mainly around agriculture. Madison County was one of the largest cotton-producing counties in the state of Alabama, and textile mills operated around the county.
This all changed when a group of German rocket scientists, led by Wernher von Braun, came to Huntsville in 1950. They developed the Mercury-Redstone Rocket, which eventually became the first vehicle to launch an American into space. Tens of thousands of jobs came to the area as a result of the "space race", and the population of Madison County rose from 72,903 in 1950 to an estimated 2005 population of 298,192..
-From Wikipedia