SR 43 used to connect Michigan City and Solsberry. It followed SR 46 through Spencer,
US 231 from Spencer to West Lafayette, and US 421 from Reynolds to Michigan City, along with its split sections. The early 1950s renumbering of Indiana highways caused SR 43 to be concurrent. US 421 was extended into Indiana in 1951, and US 231 was commissioned in 1952. SR 43 was concurrent with US 421 until the northern terminus was truncated to Reynolds in 1955 in favor of US 421. A large portion of SR 43 from Lafayette to Spencer was eliminated in 1981 in favor of US 231. In Lafayette, SR 43 basically followed the old routing of US 231 for most of the way. The route followed old US 231, 4th Street (after Alabama Street, it was 4th Street northbound and 3rd Street southbound), the Union Street bridge over the
Wabash River, and River road after an interchange. ==Major intersections==