The circumferential route at Indianapolis was part of the original proposed Interstate system for Indiana approved on March 24, 1958. Interstate Route Number A65 applied to the beginning of the route at I-65 south of Indianapolis and running west and north to I-65 near U.S. 52 and 62nd Street. Interstate Route Number B65 represented the east and north side of the loop to I-65, near U.S. 52 north of 86th Street. The leg between I-65 adjacent to Eagle Creek Park and Zionsville was not included in the circumferential highway.
Interstate 465 was selected as the designation for the Indianapolis loop by the Indiana State Highway Department by August 8, 1958. The American Association of State Highway Officials (AASHO) approved the urban Interstate numerology for the state on November 12, 1958.
Interstate 465 superseded portions of Indiana State Road 100. SR 100 represented the original beltway along the East and West Sides of Indianapolis envisioned in the 1950s. Construction of the loop began in 1959 and the first segment opened to traffic in 1961. The entire I-465 loop was completed by 1970.1
I-465 did not directly replace all of SR 100, as a portion of the route remains along Shadeland Avenue. The expressway branches north from I-465 at Exit 48 to Warren Park. This segment was decommissioned as a state road in 1999.
Prior to 2002, Interstate 465 was also signed along the northwestern spur linking the Indianapolis Beltway at Zionsville with I-65 at Royalton. Locally known as the Dog Leg, the 4.72 mile long connector was renumbered as Interstate 865. Approved by the American Association of State Highway and Transportation Officials (AASHTO) on December 15, 2002, the change addressed motorist confusion and preceded completion of the Indianapolis Advance Traffic Management System (ATMS):
Over time this section of Interstate has been labeled by the media and the motoring public as the “I-465 Connector”, “I-465A” and the “465 dogleg”. This is the very source of confusion that we wish to correct.