O scale was the dominant size, with a ratio of 1:48. However, in the early 20th century, a growing demand for more compact ...

Model trains are measured using: Scale, which tells you the ratio of your model train compared with a real one. An O scale model train is 1:48, so 1 inch on the model equals 48 inches on a real train.

O scale trains are 1:48 size models. While there are larger model railroad museums, Gribbell says he believes this is the biggest O scale model one. "There's some bigger ones in HO scale.