On February 23, 1910 , two Great Northern Railway trains--the "Seattle Express" local passenger train No. 25 and Fast Mail train No. 27--were stalled on the tracks at the Cascade Tunnel Station on Stevens Pass, thwarted by heavy snows and slides. By late the following evening, crews were able to move enough snow to allow the trains to pass westward over the summit through the Cascade tunnel, where they were stopped again just past Wellington, a small railway town where many Great Northern employees lived. As the train sat under the slope of Windy Mountain and above Tye Creek, crews worked around the clock to clear the snow but were unable to keep up with the continuous heavy snowfall and frequent slides. The situation was complicated by insufficient coal to run the plows, tired and underpaid snow shovelers walking off the job, and the loss of communications when telegraph lines went down. On the last day of February, an electrical storm arrived, bringing winds, thunder and lightning, all threats to the stability of the varied layers of snow on the mountainside. Previous clear cutting and forest fires had cleared the slopes above the tracks, contributing to the ideal conditions for an avalanche. During the early hours of March 1, either thunder or lightning caused a break in the integrity of the heavy top slab of snow; as the weaker layers below gave way, the enormous slab began to slide down the slope, carrying with it everything in its path. The avalanche pushed both trains 150 feet down into the Tye River Valley, where the cars were buried in snow and debris. Ninety six people died--thirty-five passengers and sixty-one railroad employees-- making the Wellington avalanche one of the worst train disasters in United States history. Over the following days, rescue crews transported bodies down the mountain on toboggans; the injured were taken to Wenatchee. The last of the victims was not recovered until the end of July.

The Great Northern Railway Company spent three weeks repairing the tracks before trains were able to run over Stevens Pass again. In the aftermath of the disaster, the town was renamed Tye to avoid the negative associations of the name Wellington. By 1913, the Great Northern had constructed snow-sheds over the nine miles of tracks between Scenic and Tye to protect trains from snow slides. The depot at Wellington was closed with the opening of the New Cascade Tunnel in 1929.

In the immediate aftermath of the disaster, accusations against Great Northern by the survivors, the labor unions, the press and the public became so intense that a coroner's inquest was held to determine officially whether human fault played a role in the disaster. Though the verdict placed the cause of the accident "beyond human control," it also listed three points of criticism--the insufficiency of coal, the laborers' low wages, and the decision to place the train in an unsafe location--which could be used for future lawsuits against Great Northern. Indeed, the company subsequently had to contend with a flood of legal claims from victims' relatives, freight customers, and employees. The company resolved some of these claims without admitting liability by making humanitarian payments to families. Eventually the Great Northern legal team brought a test case to trial--a $40,000 claim brought on behalf of a child whose father died in the disaster. Though the jury ruled in favor of the plaintiff, the verdict was reversed on appeal, and the Great Northern Railway Company was ultimately found not negligent or liable for the disaster at Wellington.