When doing some research on a locomotive, I came across this web site by David K Smith where he provides a history of the early years of N scale. He starts back in the late 1800's with all of the different gauges that led up to the formal adoption of 1:160 scale in the early to mid 1960's. His timelines end in 1969-1970 when N scale arrived on shores in the U.S. He even does a good job of explaining what n scale and n gauge mean. Definitely an interesting read!
Check it out: http://davidksmith.com/birth-of-n/index.htm.