Resident Population in St. Johns County, FL was 346.32800 Thous. of Persons in January of 2025, according to the United States Federal Reserve. Historically, Resident Population in St. Johns County, FL reached a record high of 346.32800 in January of 2025 and a record low of 31.03500 in January of 1970. Trading Economics provides the current actual value, an historical data chart and related indicators for Resident Population in St. Johns County, FL - last updated from the United States Federal Reserve on May of 2026.