Jefferson Island is an unincorporated community in Madison County, in the U.S. state of Montana.[1]
Montana Highway 359 passes through the community. It is about 1 mile south of Cardwell. The Jefferson River flows to the north.
A post office was established as Lahood in 1909, the name was changed to Jefferson Island in 1912, and the post office was discontinued in 1954.[2] The community took its name from a nearby river island in the Jefferson River.[3]
45°51′03″N 111°56′26″W / 45.85083°N 111.94056°W