Resident Population in Allegan County, MI was 121.93900 Thous. of Persons in January of 2023, according to the United States Federal Reserve. Historically, Resident Population in Allegan County, MI reached a record high of 121.93900 in January of 2023 and a record low of 66.57500 in January of 1970. Trading Economics provides the current actual value, an historical data chart and related indicators for Resident Population in Allegan County, MI - last updated from the United States Federal Reserve on May of 2024.