The DDA40X locomotive was called the Centennial Locomotive because the first model participated in the celebration held 100 years after the transcontinental railroad was completed at Promontory Summit, Utah, on May 10, 1869. This type of locomotive used two diesel engines on a single frame, with a passageway between the engines in the center. Union Pacific locomotive #6916 hauled priority freight between Ogden, Utah and Omaha, Nebraska, as well as to Los Angeles and the Northwest. Built in 1969 and retired on May 16, 1985, it weighed 542,432 pounds, measured 98 feet, 5 inches long, and used two 3300-horsepower General Motors Electro-Motive Division 645E3A V-16 diesel engines. The DDA40X was the last of the giant locomotives, as railroads later achieved power by linking smaller locomotives into multiple units, or MUs.