Resident Population in Grundy County, IA was 12.38400 Thous. of Persons in January of 2023, according to the United States Federal Reserve. Historically, Resident Population in Grundy County, IA reached a record high of 14.40000 in January of 1979 and a record low of 11.95700 in January of 1991. Trading Economics provides the current actual value, an historical data chart and related indicators for Resident Population in Grundy County, IA - last updated from the United States Federal Reserve on May of 2024.