Railroad mainlines at Allentown, Washington, in 1927. Joint facilities view looking north at Northern Pacific/Great Northern mainline, left, Pacific Coast/Chicago Milwaukee St. Paul and Pacific Railroad mainlne center, Union Pacific mainline and semaphore signals, right, Chicago Milwaukee St. Paul and Pacific Railroad trolley wire, covered road bridge. Photo by James Fisher. Other Subject Classes: railroad mainline, railroad signaling, railroad electrification, miscellanea.