Edited from Wikipedia
A dome car is a type of railway passenger car that has a glass dome on the top of the car where passengers can ride and see in all directions around the train. It also can include features of a coach, lounge car, dining car or observation. Dome cars were primarily used in the United States and Canada, though a small number were constructed in Europe for Trans Europ Express service.
In North America, dome cars were manufactured by the Budd Company, Pullman Standard and American Car & Foundry. Southern Pacific Railroad built its own dome cars in their Sacramento, Calif., shops.
In the 1990s, Colorado Railcar began producing dome cars. Generally, seats in the dome were considered “non-revenue” like lounge car seats. When dome cars operate today in excursion trains, the dome seats often command a premium fare.
A portion of the car, usually in the center of the car offset towards one end, is split between two levels. This resulted in the floor plan having a “long end” and a “short end” on the main level. Stairs would go up to the dome and down to the lower level.
The lower level below the dome usually contained the car’s restrooms or a small lounge area, while the upper portion was usually coach or lounge seating within a “bubble” of glass on the car’s roof. Passengers in the upper portion of the dome were able to see in all directions from a vantage point above the train’s roofline.
Union Pacific Railroad operated dome dining cars. These cars had a kitchen in the “short end” with a pantry in half the space under the dome. The other half of the space under the dome was a private dining room for small groups. Between the pantry and kitchen there was a dumbwaiter to transfer items between the kitchen and the dining area in the dome portion of the car. The “long end” was the main dining area.
Although the design of a dome car can be likened to a cupola caboose, the dome car’s development is not directly related. The earliest documented predecessor of the dome car was first developed in the 1880s; known at the time as the “birdcage car”, it was used on an 1882 sightseeing tour on the Chicago, Burlington and Quincy Railroad.
In 1891, T. J. McBride received a patent for a car design called an “observation-sleeper”; illustrations of the design in Scientific American at the time showed a car with three observation domes. Canadian Pacific Railway used “tourist cars” with raised, glass-sided viewing cupolas on their trains through the Canadian Rocky Mountains in the 1920s.