This group is open to all who are interested in American OO gauge model trains, which were primarily manufactured in the period 1934-54 by companies including Lionel, Scale-Craft, Nason Railways, Graceline, Famoco, Schorr, J-C Models, Picard, and many other smaller firms. American OO is 4mm scale (1/76) running on 19mm (3/4 inch) gauge track, just about half way between HO (1/87) and S (1/64) scales in size. American OO is also sometimes referred to as American 00 (with two zeros), but most published sources back in the day and today use the term American OO, pronounced "double O."

The photo on this page was taken on the layout of John Ericson, showing a Scale-Craft 4-6-0 with a Nason 2-8-0 tender, freight cars by Famoco and Scale-Craft, and diesels kitbashed from overscale HO models. The track is handlaid with Code 100 rail.

While Lionel did produce a three rail line in OO with center third rail, American OO is in general not a toy train scale and is not to be confused with O-27; O-27 models run on O-gauge 27 inch diameter curves and have bodies built to be generally similar to S-scale.

This group welcomes all with an interest in building, collecting, and operating American OO gauge models.