O-Gauge trains were originally called 0-Gauge because they were smaller in size then Gauge 1 (now known as G-Gauge). Train manufactures quickly realized that the smaller scales were more popular and O-Gauge was born. When the Great Drepression hit America, the demand for the more expensive & larger trains dropped and O-Gauge quickly became the mainstay of model railroaders.
Early O trains were developed with play value in mind and as a result many O trains were not strctly O, but came close enough for most people. After World War II O-Gauge manufactures started to adhere more strictly to the measurements of it's scale. This move towards realism came a little too late and by the 1960's HO trains had become more popular then O-Gauge. Sales dropped and the future of O-Gauge trains looked dim.
Since the 1990's, O-Gauge trains have been experiencing a surge in popularity. Children of all ages have fallen back in love with trains thanks to TV's Thomas the Tank Engine. The size and durability of O-gauge trains have made this scale a perfect match for little engineers. Also, because of it's size, it is easy for manufactures to put sound effects inside the trains. Many current manufactures have been making the move to digital control and are moving away from the old-school toy look of O-Gauge's history. These and other moden advancements have helped ensure that O-Gauge trains will be around for years to come.
Gauge or Scale?
What exactly is scale and gauge? These two terms often confuse beginning railroaders. The term scale is used in reference between the size of the real train versus the size of the model train. O-scale means that the train in question has a scale ratio of 1:48. O-Gauge is used when determining the distance between the two outside rails of the track.
Scale Example: The train on the left is a full-scale train and the train on the right is an O-Scale Train.
Gauge Example: the track on the left is a real-life narrow gauge track and and the track on the left is O-gauge model railroad track.