The Dalles was...if I recall correctly..the crew change and engine service facility during the steam era. The area was also big in lumber and fruit and likely a large yard for that traffic. Hood River also had a yard for the fruit traffic. A lot of things changed when, in the diesel era, Hinkle yard was developed, fruit almost totally stopped going by rail and the dams caused alot of main line and yards to be relocated. (Arlington OR comes to mind).
Roger B