Alger County is a county in the Upper Peninsula of the U.S. state of Michigan. As of the 2020 Census, the population was 8,842. It is the state's second-largest county by area, including the waters of Lake Superior. The county seat is Munising. Alger County is home to Pictured Rocks National Lakeshore, which features rock formations, waterfalls, and sand dunes along the shore of Lake Superior. Much of the county is also part of the Hiawatha National Forest.