The Rev. George Gardner Monks, 80, canon of Washington Cathedral from 1947 to 1957, died Thursday at the Maine Medical Center in Portland after apparently suffering a heart attack.

After his ordination in 1925, Mr. Monks served for a year as curate at All Saints Episcopal Church in Worcester, Mass.

He was the first headmaster of the Lenox School in Lenox, Mass., which was founded in 1927, and served there until 1946.

After leaving Washington in 1957, he served as canon of St. Paul's Cathedral in Boston until 1964.

Mr. Monks moved to Maine in 1965, to go into the real estate and investment business with his sons.

He had served in the Army in World War I in a machine gun battalion.

He was born in Boston. He graduated from St. Mark's School in 1917, and in 1921 received a bachelor's degree from Harvard University. He then attended Union Theological Seminary in New York City and Balliol College in Oxford, England. In 1925, he graduated from the Episcopal Theological School in Cambridge, Mass.

On his 80th birthday, Mr. Monks presented family members with a copy of his privately published memoirs. "Beginnings."

Survivors include his wife, Katharine Knowles Monks, of the home in South Portland, Maine; three sons, George G. Jr., of Andover, Mass., Robert A. G., of Cape Elizabeth, Maine, and William F. K., of Longmeadow, Mass.; one daughter, Mrs. Austin D. Higgins, of Cape Elizabeth, 13 grandchildren and seven great-grandchildren.