Some historians have claimed that Jacques Marquette and Louis Jolliet stopped in the Erin area on their 1673–1674 journey to find the Rock River and planted a wooden cross on the summit of Holy Hill.

However, no one has been able to determine with certainty who the first explorers to visit the area were, because Jesuit accounts often do not describe landmarks with specific enough details for historians to draw definitive conclusions.

[3] The Potawatomi surrendered their claims to the land the United States Federal Government in 1833 through the 1833 Treaty of Chicago, which (after being ratified in 1835) required them to leave Wisconsin by 1838.

[7] Since its founding, Erin has been a primarily agricultural community, with dairy farming playing an important role in the local economy.

Early businesses included blacksmiths, general stores, and creameries that supported the local farmers.

In the 1860s, a Catholic priest built a log chapel dedicated as a shrine to Mary Help of Christians on the summit of Holy Hill.

In 1906, a group of Discalced Carmelite friars from Bavaria settled at Holy Hill and built a monastery in 1920.

Holy Hill has become one of the most visited Catholic pilgrimage sites in the Midwest,[3] and was made a minor basilica in 2006.