Madison is a city in Jefferson County, Indiana, United States, along the Ohio River. The population was 12,004 at the 2000 census. The city is the county seat of Jefferson County. In 2006, the majority of Madison's downtown area was designated one of the largest national historic landmarks in the United States—133 blocks of the downtown area is on the National Register of Historic Places as Madison Historic District. On August 25, 2006, a blaze severely damaged two historic downtown buildings, the Madison Elks Lodge and a former city hall building that was occupied by an insurance company.