The Interstate Highway System is a system of freeways in the United States. It was first designed by Dwight D. Eisenhower in the 1950s. The Federal Aid Highway Act of 1956 was used to pay for construction. It was mostly built from the 1950s through the 1980s, but more freeways were built later. It is now about 47,000 miles long. Some interstates have tolls, but most do not. Most interstates have rest areas every few dozen miles.