William L. Dalrymple, 80, a retired government representive for the U.S. Gypsum Co. in Washington, died of cancer Sunday at the Calvert nursing home in Prince Frederick, Md.

Mr. Dalrymple was born in Philadelphia and grew up there and in Chicago. He took a degree in architecture at the old Armour Institute of Technology and also studied at the Chicago Art Institute. He was in private architectural practices in Illinois, Tennessee, Texas and Minnesota before returning to Chicago, where he joined U.S. Gypsum in 1937.

He was transferred to the company's Washington office in 1940 and represented it in dealings with the government until he retired in 1965.

Mr. Dalrymple and his wife, Gertrude, made their home in Bethesda when they moved to the Washington area.They lived there until 1965, when they moved to the Scientists' Cliffs community in Port Republic, Md. Mr. Dalrymple was chairman of the building committee of the Scientists' Cliffs Association until 1978 and his hobby was helping friends and neighbors remodel their summer homes in the area.

He was a member of the Chevy Chase United Methodist Church in this area and of the Christ Church in Port Republic.

In addition to his wife, of Port Republic, survivors include two sons, William L. Jr., of Nogales, Ariz., and James C., of Poolesville, and three grandsons.

The family suggests that expressions of sympathy be in the form of contribution to the Chevy Chase United Methodist Church, or to Christ Church, Port Republic.