Efforts to connect California and Oregon by rail were initiated as early as 1863. Early surveys of the Siskiyou Mountains determined that the winding, deeply incised channel of the Sacramento River was the most viable route through the southern portion of this barrier between Califonia and Oregon.

Over two decades passed before the Southern Pacific Railroad reached the southern border of Siskiyou County in 1886. A railroad camp named Pusher was built just south of the Dunsmuir Historic Commercial District.

This embryonic station was renamed Dunsmuir. By October, a roundhouse, machine shop and division superintendent's headquarters had been built. Simple wood frame business buildings were built west of the track along what became known as Sacramento Avenue.

On December 17, 1887 the last spike was driven in Ashland, Oregon, extending Southern Pacific's network of tracks from Portland to New Orleans. The rugged stagecoach journey between Portland and Sacramento, that had taken seven days to complete in 1869, had been reduced to thirty-eight hours on the iron horse.

Dunsmuir's strategic location midway between Portland and Sacramento and its position at the southern end of severe grades and curves up the Siskiyou Mountains into Oregon, made the town a logical choice for the headquarters of all railroading activities on the Shasta Route. Engines were repaired, locomotives and train crews were assigned, and "helpers" (extra engines) were added to trains to help them climb the steep 2.2% grade out of the Siskiyou Canyon.

At the height of the town's close association with the railroad in the early 20th century, nearly 2,000 men were on the Dunsmuir switching yard payroll.

The Shasta Route occupies a unique position in railroading history due to seemingly insurmountable engineering difficulties caused by heavy seasonal rain and snow, and the scenic spectacle provided by Mount Shasta and the Siskiyou Mountains. Numerous bridges, severe track curvatures, and sixteen borings were among the engineering feats necessary to traverse the 4,135 foot Siskiyou Summit.

In the words of railroad magnate Charles Crocker, "The Sierra Nevada Mountains, which first confronted me, were nothing compared with the Siskiyous for sublimity of achievement and scenery and wonderful engineering skill."

Source: Adapted from the NRHP Nomination Form submitted in 1982.

The 97-acre Dunsmuir Historic District contains thirty-two contributing buildings and three contributing structures.