originally planned as far back as 1929, the mid-county expressway was later proposed by the pennsylvania turnpike commission as the "chester extension" of the pennsylvania turnpike in 1954. after the advent of the interstate highway system, the project was transferred to the pennsylvania department of highways to be built as part of the system, designating it first as interstate 495, and later as interstate 480, as i-76 was designated as i-80s at the time. the present-day i-476 designation was assigned on february 6, 1964, when i-80s was renumbered as i-76.