During the 1960s, the demand for high HP locomotives drove EMD and competitor GE to continue to push the limits of locomotive design. During the time when 3,000 HP 16-cylinder prime movers were the norm, EMD made the decision to introduce a 20-cylinder, 3,600 HP design. Introduced in 1965, the SD45, with its distinctive flared radiator design, was purchased by many major US railroads, totaling over 1,200 units until the SD45-2 replaced it in the EMD catalog in 1972.