 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.{{cite web|last=weingroff|first=richard f.|title=federal-aid highway act of 1956, creating the interstate system|url=http://www.nationalatlas.gov/articles/transportation/a_highway.html|accessdate=9 
1956_in_law 84th_United_States_Congress Presidency_of_Dwight_D._Eisenhower United_States_federal_transportation_legislation