In the Superior Coal Field, men and machines became the rule as mining increasingly mechanized. While mules and horses were used in the early years, by the late 1930's most mines had mechanized loaders, conveyors, and cutters. The cutters under-cut the coal, the loaders lifted it, and conveyors on the back of the mining machine carried it away from the mined area to waiting coal cars that hauled it to the surface. Most coal cars were hauled by electric motors or locomotives, although some mines in the late 1930's still relied on mules. Electric locomotives increased the amount of coal that could be hauled from a mine in a given time, but they also increased the dangers. Even so, the Superior Mines maintained an excellent safety record throughout their history, winning the Sentinels of Safety trophy four times, for B Mine in 1933, C in 1934, D in 1937, and B again in 1938.