Indiana State Route 645 is a short east-west highway, and the southerly of two state highways beginning at US Route 231 and heading east to the Naval Support facility at Crane. The eastern end of Indiana Route 645 is a gate into the military property; near that gate along Route 645 is the tiny town of Burns City. The route runs in Martin County, except for the west end sitting in Daviess County. The route runs south of Crane and southeast of Odon, in southwestern Indiana.