Pendleton resident Micah Engum was exploring the McKay Reservoir earlier this month when the water line was exceedingly low. He found something not recorded on any map.

We discovered an old railroad (apparently)... There was no rail, just the wood ties and many spikes. There was a parallel track just west of it and both I'm guessing kind of ran along side McKay Creek at one time."

The earth-and-rock dam was built between 1923 and 1927. The map below predates that and shows McKay Creek snaking below Pendleton. To the left, or west, of the creek is the railroad, which now runs parallel to the road. There is no railroad running alongside the creek.

US Geological Survey

The photos were posted to Facebook and several residents said that when McNary Dam was built the work crews constructed short-gauge railroad tracks to haul dirt and rock. When the work was finished, they pulled up the rails, but left the wood. Since the McKay Dam would no-doubt have required the help of a train to haul all the fill needed to construct the dam, it leaves little doubt a similar system would have been used.
One resident even remembers an elderly relative who worked on the dam mentioning a train in some of their stories!

When the water level in McKay Reservoir runs REALLY low, apparently you can see the pump house and old foundation of the farm house that was on the site!