Locomotive 500-A, nicknamed Sweet 'Soo,' was the first passenger diesel on the Minneapolis, St. Paul and Sault Ste. Marie Railway, or Soo Line. The 1,500 h.p. FP7 heavy passenger engine was built in November 1949 by the Electro-Motive Division of General Motors as a demonstrator, and the Soo Line acquired it in spring 1950 along with a cabless F7 booster. Numbered 500-A and 500-B, the pair were repainted in the Soo Line's maroon and gold colors. Before 1950, all Soo Line passenger trains were powered by steam locomotives, but 500-A and 500-B became the line's first diesel-electric locomotives in regular passenger service when they pulled the Soo-Dominion on May 22, 1950. Steam power on the Soo Line ended in 1955. The 500-A pulled passenger trains until the mid-1960s, then served in freight and later snow-plowing service until its retirement in 1985 after more than 1.5 million miles. Owned by the City of Ladysmith, it has been restored to its 1950 appearance. The 250,000-pound locomotive is the only streamlined Soo Line F unit preserved in Wisconsin, and it is displayed with U.S. Rail Post Office-Railway Express Agency car 552, baggage-passenger car 358, and 1st Class coach 998, all original Soo Line equipment.