Hillory A. Tolson, 85, a retired assistant director of the National Park Service and executive director of the White House Historical Association, died Aug. 23 at the Collingswood nursing home in Rockville. He had Alzheimer's disease.

Mr. Tolson, who lived in Bethesda, was born in Laredo, Mo. He served in the Marine Corps in World War I, moved to Washington and went to work for the old War Department. In 1921, he took a job with the Panama Canal Commission.

In the meantime, he studied at George Washington University, where he earned a bachelor's degree, a master's degree in business administration and a law degree. He was a member of the GW track team for four years and its captain for three.

In 1931, Mr. Tolson joined the FBI as a special agent. In 1932, he began his career with the Park Service. From 1939 to 1940, he was director of Region Three with headquarters in Santa Fe, N.M. and then returned to Washington as chief of operations. He was named assistant director in 1940 and held that post until he retired in 1963.

In the course of his career, Mr. Tolson, gained a reputation as a conservationist. He was a member of the Save the Redwoods League, the American Forestry Association and the National Council of Historic Sites and Buildings.

In addition, he was chairman of the Coronado International Memorial Commission in 1942, which settled a border question with Mexico, and was a member of the International Park Commission between Mexico and the United States. He codified the laws relating to the Park Service in 1933 and updated this work in 1963.

Mr. Tolson became executive director of the White House Historical Association in 1964 and held that post until he retired a second time in 1978.

He received the Gold Medal Distinguished Service Award from the Interior Department in 1963 and the Alumni Achievement Award from George WashingtonUniversity in 1962. He was a member of the GW Athletic Hall of Fame, a Mason and a past commander of the Interior Department Post of the American Legion.

Survivors include his wife, Charlotte N., who lives at the Collingswood facility; three children, Walter J. and Robert H., both of Fairfax, and Pamela Tolson Allen of Potomac, and three grandchildren.