With the extension of the railroad in 1903, Gardiner, Montana became a thriving entrance community for Yellowstone National Park. As new businesses opened and new homes were constructed, Yellowstone's north entrance gateway community began to grow. Civic-minded men called a meeeting to decide what they could to foster the improvement of their town. At that meeting, they decided a Union Church should be built, one that all denominations could use. Mrs. Harry Childs donated the land, while funding and construction was secured through the generosity, labor and efforts of the Gardiner residents. The original building was completed in July, 1905.
Although an interdenominational church from the beginning, legal title had to be placed somwhere. Community leaders consulted with the Rev. John Prichard, an Episcopal Minister who served southern Park County, Montana and Yellowstone National Park. They resolved to place the title in the hands of the Episcopal Diocese of Montana with the assurance that all denominations would be permitted to use the church.
During the Depression and World War II, ministry at the Gardiner Union Church was, at best, sporadic. Infrequent services of worship and usage of the Gardiner Union Church were the result of of economic hardship and gasoline rationing. After the War, however, ministry at the Gardiner Union Church would improve dramatically.
In 1945-46, a young seminarian from Princeton, Warren W. Ost, worked as a bell hop at the Old Faithful Inn. Ost offered religious services and activities for Yellowstone's visitors and employees. In the early 1950's, working with Gardiner residents and National Park Service personnel at Yellowstone's headquarters in Mammoth, Ost forged a cooperative agreement between ACMNP and the residents of Gardiner and Mammoth. That agreement proposed placing a full-time member of the clergy in Mammoth to serve both the Yellowstone Park Chapel and the Gardiner Community Church, formerly known as the Gardiner Union Church. For more than 50 years, that cooperative agreement has served the Lord Jesus Christ in Yellowstone National Park and Gardiner, Montana.