Resident Population in Yakima County, WA was 259.18500 Thous. of Persons in January of 2025, according to the United States Federal Reserve. Historically, Resident Population in Yakima County, WA reached a record high of 259.18500 in January of 2025 and a record low of 145.21200 in January of 1970. Trading Economics provides the current actual value, an historical data chart and related indicators for Resident Population in Yakima County, WA - last updated from the United States Federal Reserve on May of 2026.