Madison is a city in Jefferson County, Indiana, United States, along the Ohio River. The population was 11,967 at the 2010 census. The city is the county seat of Jefferson County. In 2006, the majority of Madison's downtown area was designated the largest contiguous National Historic Landmark in the United States133 blocks of the downtown area is known as the Madison Historic Landmark 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.