The Acorn Railroad
When I was in 7th grade, our family friends the Riskins moved to a new house which had a dilapidated 7-1/2" RR around the property. Their railroad, named the Acorn Railroad, had been built in the '60s by the previous owner and had fallen into disrepair.
I spent the summer of 1975 helping their son Paul refurbish the thing - rebuilding the track, cars, and lawn-mower-engine-powered locomotive. The rail was c-shaped steel channel and for ties we used redwood (?) 2x2s: Paul's dad got a plastic trash can and a few 5-gallon cans of creosote (which you could then buy at lumberyards), we soaked the ties in there for a couple days, then pulled them out with our bare hands!
It took several weeks before the RR was ready for the inagural run, but once we did get it running we rode that thing all day, every day.
The Riskins have moved and track is long-gone, but the memories remain: It was one incredibly magical summer for a 13 year old kid!
Here's a Google map of that house, with the train track overlaid: