The southern section of SR 431 was created when the US 31 bypass of Greenwood and Southport was built between 1940 and 1945. This section extended south along Madison Avenue from the south side of Indianapolis through Greenwood. Madison Avenue was the original routing of U.S. 31 on the south side of Indianapolis. The northern terminus of this section was at Madison's intersection with East Street, which formerly carried U.S. 31 from downtown to the south. The southern terminus was where Madison merges with existing U.S. 31 alignment in Johnson County just south of Smith Valley Road, south of Greenwood Middle School.