Tank cars hold a unique place in the history of railroad freight cars. The fledgling petroleum industry of the mid-19th Century needed a way to transport their liquid product beyond the reach of local pipelines.  When a need persists, invention is sure to follow; so the petroleum companies first built their own tank cars simply by mounting wooden tubs on railroad flat cars. By the turn of the 20th Century, iron and steel tank cars, such as this Richfield Oil car, were being designed and manufactured for the oil companies across the country.

Tank cars are a common sight on today’s railroads and are now specially designed and constructed to carry many different liquid commodities, including crude oil, corn syrup and liquid natural gas.  Unlike boxcars, tank cars such as No. 670 can only carry one specific kind of commodity, so the railroads rarely supplied these special-use cars to freight customers.   Thus, privately-owned tank cars were some of the the first types of freight cars built for and owned by the “shipper” rather than by the railroad itself.  The railroad companies simply moved the car from place to place for a fee.  The “X” designation still seen today on many freight car numbers means that it is a car owned by a company other than the railroad.  The “ROX” on this car, for example, means the car was the property of Richfield Oil, regardless of the railroad on which it might have been running.