The northern terminus is at State Road 218 in the town of Camden in Carroll County.

In August 2008, the Indiana Department of Transportation awarded Carroll County a grant of $1.2 million to be used to extend the road 3 miles (4.8 km) north, to connect with the planned relocation of State Road 25.

[citation needed] When the Glover H. Cary Bridge between Owensboro, Kentucky and Rockport, Indiana opened in September 1940, its northern end connected to a new nine-mile (14 km) stretch of state highway through Spencer County that fed traffic to State Road 66.

The Indiana Department of Highways removed 75's designation from U.S. 231 in Spencer County by 1979, along with 231's other concurrent routes throughout the state (others included S.R.

In October 2002, with the opening of the William H. Natcher Bridge and the relocation of U.S. 231, this segment of highway was again redesignated, this time as a southern extension of S.R.