After the transcontinental railroad was completed in 1869, the Oregon-California Trail ceased to exist as a migration route to the Pacific. After gold was discovered in the Black Hills of South Dakota in 1874, a gold rush began. There were two main trails into the Hills from the south, but neither passed by Scotts Bluff. One of these started from Cheyenne, Wyoming, and passed through Fort Laramie. The other, and perhaps the most used, was the Sidney-Deadwood route. A bridge across the North Platte at Camp Clark, near present Bridgeport, saved the gold seekers time from the railroad junction at Sidney.

Ranchers moved in to the North Platte Valley around 1870, and by 1872, some 60,000 head of cattle were located on Horse Creek, about 20 miles west of Scotts Bluff. [15] From this time until 1886, the cattle industry flourished in the valley. Inflation of the cattle market, overstocking, overgrazing, and the disastrous winter of 1885-86 caused the cattle industry to suffer greatly and it was not long before ranching was of secondary importance in the vicinity of Scotts Bluff. Homesteaders moved into the North Platte Valley and staked out claims in the early 1880's. Towns soon made their appearance. Gering was platted in 1888 and became a center of farming and ranching activity. Other towns soon came into being.

The last large town to be platted was Scottsbluff. When the Burlington railroad reached up the valley on the north side of the river in 1900, a rush was started to build along this route across the river from Gering. Ten years later the Union Pacific railroad came up the south side of the river. The Burlington had a jump on the people on the south bank of the North Platte, however, and Scottsbluff steadily grew into the largest town in the County of Scotts Bluff. Today, Scottsbluff has a population about 14,000, while Gering, the county seat, has about 5,000.

During the late years of the nineteenth century, the old Oregon Trail was used mostly by the military between Forts Kearny and Laramie, for cattle drives, and by freighters, ranchers and farmers, and travelers between the communities which had sprung up along the south bank of the North Platte. The Oregon-California Trail soon became a part of history.

First interpretive marker was placed in Mitchell Pass by the State of Nebraska in 1912, seven years before the Monument was established.