Resident Population in Kittitas County, WA was 48.17200 Thous. of Persons in January of 2024, according to the United States Federal Reserve. Historically, Resident Population in Kittitas County, WA reached a record high of 48.17200 in January of 2024 and a record low of 24.40000 in January of 1977. Trading Economics provides the current actual value, an historical data chart and related indicators for Resident Population in Kittitas County, WA - last updated from the United States Federal Reserve on April of 2026.