When passenger trains were still the preferred mode of intercity transportation in America, observations often were used by those campaigning for public office, especially for the Presidency of the United States. The candidate's train would pull into town and stop with the observation end at the station, then the candidate would appear on the observation's platform to deliver his "stump speech". The observation platform made a perfect temporary stage for just such an event.
Industrial design
While the cars manufactured by companies such as Pullman-Standard conformed to somewhat standard designs, some railroads created their own distinctive designs for ovservation ends. For example, the Milwaukee Road's passenger trains were often rounded out with either a Skytop Lounge or a Beavertail observation. The Milwaukee's observations were easily recognizable as the observation end of the cars were not only rounded, but also slanted toward the front of the car, often with windows extending up from the normal window height to the roofline.
The Western Pacific Railroad built combination dome-observation cars for use on the California Zephyr. The railroad touted this combination car type as "the best of both worlds" in passenger amenities.
External links
Dome Observation history (http://calzephyr.railfan.net/cars/domeobs2.html)
A portion of the car, usually in the center of the car, is split between two levels, with stairs leading both up and down from the train's regular passenger car floor level.
On some domecars, the lower portion was outfitted with a galley, where car attendants used dumbwaiters to transfer items between the galley and a dining area in the dome portion of the car.
As domecars became more common on North American passenger trains, some western railroads purchased or built "superdomes." These were domecars where the upper level of the car extended for nearly the entire length of the car.