A brief background of O-scale
We are often asked, "Is Lionel O-gauge the same thing as O-scale "? "Can one locomotive operate on either O-gauge or O-scale track"? The answer is "not very well". While both O-gauge and O-scale are similarly proportioned at 1:48, or 1 inch small train equals 48 inch on a real train (prototype), and while the distance between the rails is the same, other factors of design are different.
Little trains or toy trains became popular as early as 1880 or shortly after electricity was commercially available to power them. Prior to 1880, there were even a few "wind up" toy trains powered by a compressed spring.
By 1912, the Lionel Corporation mass-produced toy trains designed to run on O-gauge track. Gauge refers to the distance between the outer rails, measured from their inner sides. Scale refers to the size relationship between the model and a real train (prototype). Lionel and other early toy train producers were concerned only with gauge and not with scale. Competing toy train makers (Ives, Gilbert, Marx, Marklin and others) wanted their own exclusive gauge of track so there could be no interchanging of models. They reasoned that if you buy their toy train you must also buy their tracks.
By 1930, Lionel's exclusive O-gauge was the most popular size surpassing Lionel's larger and earlier size that was called Standard Gauge. But toy train manufacturers made no effort to model their trains or tracks to scale which was considered unimportant. This meant most cars were too short (for scale), there was too much space between cars, the couplers were far too large, the track was tubular, hollow and oversize, and a third rail between the running tracks was required. The market for toy trains was defined as children, thus the trains layouts had to be fast and easy to assemble and operate. There could be no intricate wiring as when a track without a center "power" rail loops back on itself creating a "reversing" polarity loop. The child's imagination could make up for the lack of proportion to the prototype (scale).
Surprise, surprise! Not all end users of Lionel or other toy trains were children. Adults bought them for themselves and some adults made an effort to model to scale, a frustrating experience at the time. Gradually, a few specialty manufacturers began to produce locomotives, cars and track in O-scale. While the gauge did not change, the design and proportions of almost everything else did. Model railroading was born when O-gauge became O-scale.
Today, the so-called "toy" trains of O-gauge are still popular and manufacturers are building O-gauge locomotives more to scale. O-gauge remains the overwhelming favorite for children and adults who want lots of train action in easy-to-assemble form. Much of these layouts can be covered with action accessories such as log or coal loaders, moving crossing guards, lights, bells and whistles. It's fast moving and fun.
Should the train operator want to move more deeply into modeling, with extreme attention to locomotive and equipment detail or scenic landscaping, then the move is often made to O-scale. Modeling is a joy to some, but too tedious for others.
O-gauge became the earliest widely used gauge for scale modeling. Since the 1930's, smaller gauges have been created for modeling, including HO scale (proportion 1:87) and N scale (proportion 1:160). Neither HO nor N scale trains were ever produced as "toy" trains. From their beginning, they were produced for modelers. In addition to the SDMRRA O-scale layout, the San Diego Model Railroad Museum features two distinct and different layouts in HO scale plus one layout in N Scale. The museum also features a Lionel Toy Train Gallery in O-gauge.