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