Operating Era: 1899-1970. Great Northern, Algoma Central, Lake Champlain & Moriah, Yosemite Valley, Sierra Railroad. A spinoff of the technology used for its all-steel hopper car, Pressed Steel Car Co. developed 40- and 50-ton ore cars in 1899. Most cars were sold to Lake Superior District roads in 1899-1901. They were so well built that used ones were used for decades after advancements made them obsolete for first class roads. Some still exist today. Hopper mold has been reworked to greatly improve quality of castings.