Meriwether Lewis named the Dearborn River for Thomas Jefferson’s secretary of war, Henry Dearborn, when the Corps of Discovery encountered the “handsome, bold and clear stream” in 1805. Lewis described it as:
“being nearly as wide as the Missouri at that place. Its current is rapid and water extremely transparent, the bed is formed of small smooth stones of flat, rounded or other figures. … It appears as if it might be navigated, but to what extent must be conjectural.”
Lewis also noted the extensive timber in the drainage. Turn-of-the-last-century loggers worked the area, taking much of the ponderosa pine. Many pines, too twisty to mill, have grown into huge, gnarled sentinels that wave their branches from the surrounding hills. U.S. Army topographer P. M. Engel passed through in 1859 scouting the route for John Mullan’s military road. He described the remote timbered valley as difficult to maneuver, “…cut up by a great many sloughs and ditches.” Homesteaders later began to settle in the area with the completion of the Montana Central Railroad in 1887. Augusta, strategically located between Helena and Great Falls, was established as the local trading center. In 1889 Montana became a state, and four years later in May of 1893 the town site of Augusta was surveyed and dedicated. It was named after the first child born in the town, Augusta Hogan, daughter of an early rancher, D.J. Hogan.
Built in 1897, the Dearborn River High Bridge, which sits along Montana 434, provided critical access for homesteaders to the railroad in Augusta and Wolf Creek. Prior to it being built, generations of native peoples used this crossing in their seasonal travels to the Great Plains to hunt buffalo. Until the early 1930s, local farmers and ranchers transported goods and livestock across this bridge. This structure is the last surviving example of a pin-connected Pratt half-deck truss bridge in the United States. King Bridge Company of Cleveland, Ohio, tailored the design specifically to the Dearborn River Canyon to carry relatively light loads over the deep crossing. Lewis and Clark County and the Montana Department of Transportation restored the landmark bridge in 2003.
Dearborn Canyon Overlook is located just north of the Dearborn River High Bridge.