US 421 was routed on Southeastern Avenue, Washington Street, Northwestern Avenue (now Martin Luther King Jr. Street), and Michigan Road.
•
Originally, US 421 followed Southeastern Ave. into downtown Indianapolis, where it merged with US 40 (Washington St.) to West Street, then turned north, following West Street, Northwestern Avenue (later Martin Luther King Jr. Street), and Michigan Road up to the northwest side of the city.
Indiana | Indiana University | Indiana Jones | Fort Wayne, Indiana | Evansville, Indiana | South Bend, Indiana | Allen County, Indiana | Terre Haute, Indiana | U.S. Route 66 | U.S. Route 1 | Indiana State University | Bloomington, Indiana | Gary, Indiana | Vincennes, Indiana | U.S. Route 6 | U.S. Route 101 | Indiana University Bloomington | Indiana Jones and the Temple of Doom | Route 66 | U.S. Route 30 | New Jersey Route 4 | European route E65 | U.S. Route 40 | California State Route 1 | Valparaiso, Indiana | Indiana House of Representatives | Governor of Indiana | Aboite Township, Allen County, Indiana | Wayne Township, Allen County, Indiana | U.S. Route 1 in Maine |