Re: Why three feet?

George Hilton in his epic book, American Narrow Gauge Railroads, devotes the first chapter to "The Origins of the Narrow Gauge Movement." He discusses the development of standard gauge, the problems of the broad gauge lines in England, and then the development of narrow gauge.

The first significant narrow gauge is the still operating Festiniog. Even with its success, the very narrow gauge (1'-11-1/2") of the Festiniog was seen as disadvantageous and various writers proposed 2'-6", 2'-9" 3'-0", and then 3'-6". The gauge of 3'6" was soon adapted for use in various British colonies and in time it became known as "Imperial Gauge."

The narrow gauge proponent Robert Fairlie soon accepted 3'-0" as the best of the narrow gauges and promoted it. Soon other writers were also proposing 3' instead of other gauges. And by the end of 1871 there were two 3' gauge lines in the American south, one at Pittsburgh and the beginning of a major system at Denver, Colorado.

Brian Norden