In US railroad terminology, a gondola is an open-top type of rolling stock that is used for carrying loose bulk materials. Because of its low side walls, gondolas are used to carry either very dense material, such as steel plates or coils, or bulky items such as prefabricated pieces of rail track.
Before the opening of the Baltimore & Ohio Railroad and the Chesapeake & Ohio Canal in Harpers Ferry, Virginia (now West Virginia), considerable amounts of coal were carried via the Potomac River. Since timber was an abundant resource, flat boats, called "gondolas" (a spoof on Venetian rowing boats), were constructed to navigate the "black diamonds" down river to markets around Washington, DC. There, both the boat and cargo were sold and the boatmen returned home by foot. The railroad cars first employed in the haulage of coal were thus named after these shallow-draft boats called "gondola cars".
Early gondola cars typically had low sides. Their contents had to be shoveled out by hand, and they took a long time to unload. In 1905, the Ralston Steel Car Company patented a flat bottom gondola with lever operated chutes that allowed the gondola to be unloaded automatically from the bottom. The chutes would direct the contents of the gondola to the sides. This coincided with the switch from wood to steel freight cars, as the pulling force of locomotives tended to crush the older wood cars.
Specialized car types
Lorry or Mine car
The first railway bulk-cargo gondolas, indeed the first freight wagons, were the chaldron cars of the early coal-carrying plateways. These were relatively short and tall in proportion, with a tapered body that widened upwards, above the wheels. Once locomotive haulage began, the unstable and top-heavy nature of this design became a problem with increasing speeds and later wagons became lower and longer. The chaldron shape survived in a few cases, such as low-speed working around a large factory site, such as a steelworks.
In the second half of the 20th century, coal haulage shifted from open hopper cars to high-sided gondolas. Using a gondola, the railroads are able to haul a larger amount of coal per car since gondolas do not include the equipment needed for unloading. However, since these cars do not have hatches for unloading the products shipped in them, railroads must use rotary car dumpers (mechanisms that hold a car against a short section of track as the car and track are slowly rotated upside down to empty the car) or other means to empty them. The term "bathtub" refers to the shape of the car.
Track ballast gondolas
Track ballast gondolas carry ballast.
- Double Stack Intermodal Cars-Freight 
- Origins of name in railroad use 
- In Australia these wagons are called open wagons.
- Atchison, Topeka and Santa Fe Railway #72312 — photos and short history of an example of a typical steel, four-axle, solid bottom, fixed end, mill gondola.
- Guide to Railcars