Washington Street is the primary east–west street in Indianapolis, Indiana, United States. The street follows the route of the National Road for almost all of its length in the city of Indianapolis. For a time, its entire length was designated as U.S. Route 40 before that route was re-aligned with the southern segment of Interstate 465; now only the segments of Washington Street between I-465 and the city limits on either side of the city are part of U.S. 40. The street delineates north–south address numbering for the eastern two-thirds of the city; Rockville Road separates north and south from the western border of the city until it meets Washington Street in Wayne Township at Tibbs Ave. Washington Street begins in the west at the intersection with Raceway Road. As it heads east–northeast it passes by the Indianapolis International Airport, which lies to south. Immediately thereafter it has an interchange with I-465 on the west side of the city, where U.S. 40 diverges. After merging with Rockville Road, Washington Street heads more directly east toward downtown Indianapolis. Approaching downtown it passes the Indiana Medical History Museum on the former site of Central State Hospital for the Insane; it then passes the headquarters of the Indianapolis Public Transportation Corporation, which is in buildings that once housed the Duesenberg Automobile and Motors Company.