Mennonites arrived at Mountain Lake in 1873. Mennonites are a Protestant Christian group with sixteenth century European origins. Their name refers to Menno Simons, who was a Dutch religious reformer. Simons preached a fundamentalist, more literal interpretation of the Bible. He also emphasized the importance of adult baptism. Along with these beliefs, Simons promoted a simple way of life similar to Jesus Christ and the apostles. As part of his creed, he stressed the importance of Christian brotherhood, pacifism, and the primacy of family in Christian life. The tenet of pacifism played a significant role throughout Mennonite history.

The Treaty of Traverse des Sioux (1851) between the Sisseton and Wahpeton bands of Dakota and the US government transferred ownership of much of southeastern Minnesota Territory to the United States. Along with the Treaty of Mendota, signed that same year, it opened twenty-four million acres of land to settler-colonists. For the Dakota, these treaties marked another step in a process that increasingly marginalized them and dismissed them from the land that had been—and remains—their home.