During the Copper mining boom of the late 1800s and early 1900s, thousands of Finns immigrated to the Keweenaw and other areas of the Upper Peninsula and became an important part of the growth and development of the region. The descendants of many of the original Finnish copper miners that settled in the Upper Peninsula continue to play an important role in making the area an energetic and exciting place to live, study, and work. Today, the Upper Peninsula is still home to the highest concentration of Finns outside Europe. Houghton, Keweenaw, Baraga, Ontonagon and Gogebic counties are the only counties in the United States where residents claiming Finnish ancestry are the largest single ethnic group. The Finnish sauna and the concept of sisu have been adopted widely by residents of the Upper Peninsula. Finlandia University, America's only college with Finnish roots, is located in Hancock. Street signs in Hancock appear in English and Finnish to celebrate this heritage.