45 was being extended north from Haysville to Loogootee, and a separate segment between Cincinnati in Greene County and Bloomington had also been completed.

By 1940, the entire route from Rockport to Bloomington was complete, but when the Crane Naval Ammunition Depot was commissioned in 1941, the portion of the highway between Burns City and Cincinnati had to be rerouted to the west perimeter of the installation.

The deletion left the current segment along with a short, 5-mile section from Patronville to Rockport that acted as a connector to then-U.S. 231 (now State Road 161) and Owensboro, Kentucky.

This southern section was decommissioned and turned over to the control of the city of Rockport (within the city limits) and Spencer County (outside of Rockport) in March 2001, about a year before U.S. 231 was rerouted onto the William H. Natcher Bridge.

[3] A major construction project to widen the road to four lanes in Bloomington was completed in November 2012.