Not originally part of the Federal Aid Highway Act of 1956, I-77 was added the following year as a route between Charlotte and Port Huron, Michigan, via Detroit. In 1958, the routing was realigned towards Cleveland instead; the Detroit–Port Huron section became part of I-94. I-77 received two extension approvals; the first in 1964, continuing south from I-85 to U.S. Route 74 (US 74), and the second in 1969 to the South Carolina state line towards Columbia. The Interstate was completed in 1977.