The history of coal mining in Sunnyside began shortly after Jefferson Tidwell and his three sons discovered coal in Whitmore Canyon in 1896. By 1898 the Pleasant Valley Coal Company had acquired the rights to the coal from Tidwell, and by 1901 the Denver & Rio Grande Western Railroad with its subsidiary Utah Fuel acquired the operation. For the next fifty years Utah Fuel operated the coal mines in Sunnyside and in 1949 sold its interest to Kaiser Steel Corporation. It was the financial investments of these companies that turned Tidwell's merger mining operation into a major coal industry, which became inextricably tied to Sunnyside until its demise ninety years later.