Interstate Highways The Federal-Aid Highway Act of 1956 officially created the interstate system. It was signed into law on June 20, 1956. In August 1957, AASHO announced the numbering scheme for the interstate highways and unveiled the red, white, and blue interstate shield. Many of the states had submitted proposals for the shield, but the final version was a combination of designs submitted by Missouri and Texas. Administrator Tallamy approved the route marker and the numbering plan in September. The interstate system was initially set up for military transport as well as cargo transport. However, in later years, the interstate has become open to cars as well. Alabama first showed the interstate system in 1961. The last segment was completed in 2017, with the completion of the Corridor X Project, which was designated Interstate 22.

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