Sheridan is a town in Madison County, Montana, United States named after the Civil War general Philip Sheridan. The population was 642 at the 2010 census. Sheridan is known as the "heart of the Ruby Valley." Seven majestic mountain ranges surround this beautiful community. (Tobacco Root Range, Highlands Mountains, McCartney Mountain, The Pioneers, The Ruby Range, The Gravellies and the Snowcrest Range) The geology of the area includes some of the oldest rocks dating back over 2.7 billion years.