William Copley Winslow was born on January 13, 1840, in Boston, Massachusetts.

He was an Episcopal clergyman, archeologist, and journalist. He graduated from Hamilton College, Clinton, New York, in 1862 and the General Seminary, New York, in 1865. He was ordained a deacon in 1862 and priest in 1867. He spent several months in Italy studying archeology and ancient sculpture. Upon his return, he became rector of St. George's Church, Lee, Massachusetts (1867-1870) and later chaplain of St. Luke's Home in Boston (1877-1882). Winslow's deepest interest was in archeological research. In 1880, he visited the monuments and sites of Egypt and founded the American branch of the Egypt Exploration Fund. He served as its honorary treasurer (1883), vice-president (1885), and honorary secretary (1889). As a result of Winslow's enthusiasm for making Egypt known to the American people, the Boston Museum was enriched with a notable collection of Egyptian monuments. He was an honorary Fellow of the Royal Archeological Institute, corresponding member of the British Archeological Association, honorary correspondent of the Victoria Institute, honorary Fellow of the Royal Society of Arts and Sciences, and a Fellow of the Antiquarians of Scotland. Winslow was also an honorary member of the Nova Scotia and Quebec Historical Societies and the Montreal Society of Natural History. He published numerous papers and articles on the subject of Egypt and archeology.

In 1867, he married Harriet Stillman Hayward (1835–1915), and in 1917, he remarried Elizabeth Bruce Roelofson (1862–1923). He died on February 2, 1925, in Boston, Massachusetts.