The cars used on the early railways were very much like the stagecoaches and wagons traveling on ordinary roads.
The very first freight cars are known to have been used in coal mines in England. They were open-top wooden wheels and were pulled by horses along wooden rails. They were followed by platform cars, also known as flat cars, upon which the freight was piled and covered with tarpaulin to protect it from the weather. As the goods often fell off and were fitted with low sides and ends. Later, covered cars came into existence.
As time went on and railroads had to carry more and more freight, bigger and better cars were invented for hauling different kinds of goods. Today, the railroads have several classes of freight cars, there being many varieties in each class.
A box car is considered to be most common type of covered car. It is a general-purpose car intended to carry all kinds of ordinary goods, which must be protected from the weather. A special type of box car is a refrigerator car used for hauling food products. The walls, floor and roof of this wagon are air- and waterproof to protect goods from the heat of the outside air. Another type of car is a tank car intended for liquid goods. The long cylindrical tank of the car is filled through an opening on the top and emptied through a special device in the bottom.