Green River was incorporated in 1868 in what was then the Dakota Territory. The city was the starting point from which John Wesley Powell started his famous expeditions of the Green River, the Colorado River, and the Grand Canyon in the late 1800s.

Green River was originally supposed to be a the site of a division point for the Union Pacific Railroad, but when the railroad finally reached the point, officials were surprised to find that a city had already been established there. They moved the division point 12 miles west. At the time of its incorporation in 1868. Green River had about 2000 residents and permanent adobe buildings were being built. However, when the division point of the railroad was moved west, the city shrank to a mere 101 residents. Just when the city was on the verge of shriveling up. the Black Fork dried up during a drought and the railroad was forced to move the division point back to Green River. The town was officially incorporated under the new laws of Wyoming on May 5. 1891.

The Rock Springs massacre (also known as the Rock Springs riot) occurred on September 2,1885 in the present-day city of Rock Springs, Wyoming, in Sweetwater County. The riot, between Chinese immigrant miners and white, mostly immigrant, miners, was the result of racial tensions and an ongoing labor dispute over the Union Pacific Coal Department's policy of paying Chinese miners lower wages than white miners. When the rioting ended, at least 28 Chinese miners were dead and 15 were wounded. Rioters burned 75 Chinese homes resulting in approximately $150,000 in property damage. Tension between whites and Chinese immigrants in the late 19th century American West was particularly high, especially in the decade preceding the violence. The massacre in Rock Springs was the violent outburst of years of anti-"coolie" sentiment in the United States. The 1882 Chinese Exclusion Act suspended Chinese immigration for ten years, but not before thousands of immigrants came to the American West. Most Chinese immigrants to Wyoming Territory took jobs with the railroad at first, but many ended up employed in coal mines owned by the Union Pacific Railroad. As Chinese immigration increased, so did anti-Chinese sentiment from whites. The Knights of Labor, one of the foremost voices against Chinese immigrant labor, formed a chapter in Rock Springs in 1883 and most rioters were members of that organization. However, no direct connection has ever established that the riot was caused by the national Knights of Labor organization. In the immediate aftermath of the riot, federal troops were deployed in Rock Springs. They escorted the surviving Chinese miners, most of whom had fled to Evanston, Wyoming, back to Rock Springs a week after the riot. Reaction came swiftly from the era's publications. In Rock Springs, the local newspaper endorsed the outcome of the riot, while in other Wyoming newspapers, support for the riot was limited to sympathy for the causes of the white miners The massacre in Rock Springs touched off a wave of anti-Chinese violence, especially in the Puget Sound area of Washington Territory.