SR 124 starts in Peru at the corner of Broadway and Riverside Drive. The state road heads east concurrent with Riverside Drive and parallel to the Wabash River. The road leaves Peru and enters rural Miami County, passing through farmland. SR 124 parallels the Mississinewa River, before crossing over it. After crossing over the river SR 124 passes north of the Mississinewa Lake Dam, before entering Wabash County. In Wabash County the highway passes through mostly agricultural areas with some woodlands. SR 124 has intersection with SR 13 and SR 15 in rural Wabash County, south of the city of Wabash. East of SR 15, SR 124 enters Huntington County. In rural Huntington County SR 124 passes through an intersection with SR 105 and SR 9. After SR 9, SR 124 passes through Mt. Etna and a small section of the Salamonie River State Forest. SR 124 passes over the Salamonie River, before an intersection with Huntington County Road 300 West, formerly known as SR 221, south of Lancaster. The highway continues east passes farmland and through an intersection with SR 5. East of SR 5, SR 124 passes over Interstate 69, but SR 124 does not have an interchange. After I-69, SR 124 has an intersection with SR 3, before leaving Huntington County and entering Wells County. In Wells County SR 124 has an intersection with Wells County Road 300 West, formerly known as SR 303. West of Bluffton SR 124 turns north and then back east, crossing over the Wabash River, before having an intersection with SR 116. SR 124 turns east onto SR 116 and the roadway heads east towards SR 1. The highway has an at-grade crossing with a Norfolk Southern Railroad track, before entering the city of Bluffton. At SR 1 both SR 116 and 124 turn south concurrent with SR 1, passing through Bluffton as a four-lane highway. The highway passes commercial properties and has an at-grade crossing with a Wabash Central Railroad track. SR 124 turns east and leaves Bluffton. East of Bluffton SR 124 passes through farmland and has an intersection with SR 201, before passing north of Ouabache State Park. The road has an intersection with SR 301 in rural Wells County, before crossing into Adams County. SR 124 has an intersection with U.S. Route 27, west of Monroe. The road enters Monroe concurrent with Washington Street, passing south of Adams Central Community Schools and through a mostly residential area. The road leaves Monroe and reenters rural Adams County. The highway has an intersection with SR 101, before crossing over the St. Marys River. After crossing the river the SR 124 designation ends at the Ohio state line. The roadway continues east as Ohio State Route 81 and passes through the village of Willshire, Ohio.
History
The Indiana State Highway Commission designated SR 124 as a state road in early 1932, between SR 5 and the Wells–Adams county line. SR 124 in Adams County became a state road in late 1932. In 1934 the route between Peru and SR 5 was authorized to become a state road. Between late 1938 and early 1939 the route between the Miami–Wabash county line and SR 5 officially becomes a state road. SR 124 in Miami County was added to the state road system in late 1950 or early 1951. Paving on SR 124, in Miami and Huntington county and between SR 1 and the Wells–Adams county line, was completed in late 1962 or early 1963. The rest of the route was paved between late 1965 and early 1966. A bypass around the west side Bluffton was completed in late 2003 or early 2004.
