The Federal-Aid Highway Act of 1956, also known as the National Interstate and Defense Highways Act, Pub. L. 84–627 was enacted on June 29, 1956, when President Dwight D. Eisenhower signed the bill into law. With an original authorization of $25 billion for the construction of 41,000 miles (66,000 km) of the Interstate Highway System over a 10-year period, it was the largest public works project in American history through that time.