Railroad through the Rocky Mountains
Hopping Jenny is the band.
Key of D. Three parts? Seems like there is a short middle part. This tune is sometimes called Railroad across the Rocky Mountains.
Jim Bowles from Kentucky [recording at Slippery Hill].
BattleAxe Band [bandcamp] nice recording with a different chord.
Solo fiddle by Tobias Enevoldsen [utoob].
Not to be confused with...
Across the Rocky Mountains is a different tune by Roscoe Holcomb.
Springtime in the Rockies is a different tune by Leadbelly.