Railroad Pass, 2,358 ft, is a mountain pass through the Black Hills of the River Mountains in the southeastern portion of the city of Henderson, Nevada, which is part of the Las Vegas metropolitan area. Traversed by the Union Pacific Railroad's Boulder City spur of the Henderson branch line and by the Boulder Highway, the pass connects Henderson with …Railroad Pass, 2,358 ft, is a mountain pass through the Black Hills of the River Mountains in the southeastern portion of the city of Henderson, Nevada, which is part of the Las Vegas metropolitan area. Traversed by the Union Pacific Railroad's Boulder City spur of the Henderson branch line and by the Boulder Highway, the pass connects Henderson with Boulder City.