State Road 21 followed the same route as US 35 does today. SR 21's first segment was decommissioned in 1965. The second part of SR 21 followed SR 19 from Amboy to Peru; this was decommissioned in 1979.
State Road 100 no longer exists as a state highway (although it still is marked on some maps); the short final signed section on S. Shadeland Avenue was turned over to the city of Indianapolis in 1999. It was a vision to create a beltway around Indianapolis. It was deleted after having been truncated to a short route between US 40 and I-465 in the early 1990s, when all signed highways going through Indianapolis were diverted onto the I-465 beltway. The highway began just south of U.S. Route 52 at I-465. It traveled northward as Shadeland Avenue. It turned west at Castleton, in northeastern Marion County, following 82nd Street. Between State Road 37A (Allisonville Rd) and the distinctive bridge over the West Fork of the White River just east of State Road 431 (Keystone Ave), it became 86th Street. It continued on west along 86th to the far-northwest side of Marion County, where its exact route west of US 421 (Michigan Rd) is unclear. It may have once ended at the I-65/SR 334 intersection in Boone County.
There were two other short sections of Indiana 100. The first section designated as SR 100 ran from US 40 along High School Road south to the Indianapolis Municipal (now Indianapolis International) Airport. The second, a short lived section, ran along Troy Avenue from Meridian Street (then SR 135) to Bluff Road (then SR 37). This section did not survive long after the decommissioning of SR 37 along Bluff Road.
The following places were along the highway's route:
State Road 112 ran in Elkhart to U.S. Highway 20 from State Road 19 and was originally part of U.S. Highway 112 from 1926 to 1934. It has since been deleted, most of it having been incorporated into Indiana 19 as it was diverted away from downtown Elkhart.
Following Mayflower Road for its entire route, it began from its parent State Road 23, southwest of the city limits. It ran for 5 miles (8.0 km) northward, interchanging with the U.S. Route 20/U.S. Route 31 bypass at about mile 2. One half mile north of that, it sprouted its own child route to the west, State Road 223 at Grant Road. Another half mile farther north, it intersected State Road 2 (which itself has been deleted east of US 31) at West Western Avenue. It then terminated at what is now Business Route 20 two miles (3 km) north of that.
Mayflower Road still has significant traffic, but SR 123 has been turned back into this local street.
State Road 131 in the U.S. State of Indiana was the main roadway that ran for two miles (3 km) through the retail district of Clarksville until 2003, when it was turned back to the city. It is now known as Lewis & Clark Parkway.