Madison is a town in the southeastern corner of New Haven County, Connecticut, occupying a central location on Connecticut's Long Island Sound shoreline. The population was 18,812 at the 2000 census. Madison was first settled in 1641. Throughout the 18th century, Madison was known as East Guilford until it was incorporated as a town in 1826. Since then, Madison and Guilford have shared many cultural and economic similarities despite an unofficial high school rivalry.