The railroad coach with pairs of seats on either side of a center aisle, and with an open interior without compartments, became known as the 'American style' coach. (This in contrast to many European-style rail passenger cars built for day travel up through the 1930s - and even more recently - which were configured with divided compartments, a side aisle, and, in many such cars, an exterior door to the station platform for each compartment.)
The 'American style' coach is more economic, since it seats more travelers in a given length of car. Also, the fully open interior allows the conductor and other train staff easily to keep an eye on passengers' behavior in the car - a valued benefit for the safety of passengers, especially in the 19th century (but even today).
'American style' coaches, carried by eight wheels arranged in two, four-wheel bogies (called 'trucks'), came as early as the mid-1830s in the U.S., i.e., within just a few years after the very first steam-locomotive-pulled trains began running in the U.S., in 1830. The two trucks, rather than just four wheels under a smaller car, gave a much more stable ride. The 'eight-wheel car' was another common term for the type. The basic style continues to this day.
Railroad coaches could be equipped for short-distance or long-distance travel. Short-distance cars, such as for commuter and 'local' trains, had plain seats, short pitch (the distance between seats fore-and-aft), and very plain interiors. Coaches for long distances had more comfortable seats, longer pitch, and perhaps a bit more elegance in interior appointments.
Seats in both types of coaches were reversible, so the car could go in either direction with its seats facing forward, and to allow train staff to turn some seats to face one another if passengers so requested.