He served on the California State Park Commission 1934-1960 and was chairman 1938-1960. He was appointed by Governor Earl Warren as chairman of the California Centennial Commission, 1948 - 1950. Knowland was honored September 9, 1951 by the City of Oakland and the State of California, with Joseph Knowland State Arboretum and Park in Oakland. He served as chairman of the Oakland Centennial, 1952, and the Alameda County Centennial, 1953.

At 18, Knowland joined the Native Sons of the Golden West, which he served as Grand President in 1909. He organized the California Historical Landmarks League and was its chairman from 1902 to 1906. He was chairman of the Landmarks Committee of the Native Sons of the Golden West, 1902-1962. He was a member of the State Assembly from 1899 to 1903, and in the California State Senate from 1903 to 1904.

The long-time conservationist, politician and publisher of the Oakland Tribune died February 1, 1966.