The railroad Tobin Bridge is located on the Union Pacific Railroad's (originally Western Pacific Railroad's) Feather River Route through the Sierra Nevada in northeastern California, connecting the Sacramento Valley to Salt Lake City via the Feather River valley. The bridge is part of WP's eastward climb to its summit at Beckwourth Pass while maintaining the railroad's overall 1.0 percent (compensated) grade, the least steep of any mountain grade on a transcontinental railroad.