There are a number of areas in the 48 contiguous United States known informally as tri-state areas. Often, a tri-state area is an area associated with a particular town or metropolis that lies across three states. Some, but not all, of these involve a state boundary tripoint. Other "tri-state" areas have a more diffuse population that shares a connected economy and geography, especially with respect to climate, such as the tri-state area of Indiana, Ohio and Michigan.