When William was thirteen his father died and in 1937, due to the Ohio River flood, he and his family were forced from their home for weeks until the water subsided.

Dimmick was a graduate of Berea College and held Masters and Doctoral degrees from Yale Divinity School.

He then served as assistant bishop in Minnesota, where he exercised an ecumenical ministry at a Roman Catholic abbey and university.

[2] On April 5, 1968, the day after the assassination of Martin Luther King Jr., Memphis clergy from many churches and synagogues met at St. Mary's.

In an impromptu move, Dimmick took up the cathedral's processional cross and led the assembled ministers down Poplar Avenue to City Hall to petition Mayor Henry C. Loeb to end the Memphis sanitation strike that King was in town to help negotiate.