Union Pacific "Big Boy". The overall length of this Big Boy locomotive is 132 feet, 9-1/4 inches. It was retired by the Union Pacific in February 1962 after logging 1,029,507 miles. The locomotive cost the UP $265,000 when it was built in the 1940s. The train weighs 1,189,500 pounds and was operated at speeds of up to 80 miles per hour.