The ore car began as a relatively short 24-foot standard, owing to the weight of iron ore and the wood construction of cars in the 1880's. Both railroads rostered wooden ore cars, some built by local shops, some by Pullman Standard. By the 1910's, demand for volume of ore was such that the first steel cars were received. These cars were of 50-ton capacity. Variations existed, as each successive order of cars seemed to try out a new innovation, including rib sides, different doors, long end platforms and panel sides.

In the 1930's, capacity was increased to a 70-ton car, and from then on out, the 70-ton car followed consistent design, even though orders alternated between ACF and Pullman Standard through 1957 when the last order of ore cars was placed. Beginning in the 1960's, side extensions were added to some ore cars to increase volume capacity on cars hauling the less dense taconite pellet.