William Arthur Holt was born in Lake Forest, Illinois to Devillo and Ellen Holt. He attended Lake Forest Academy and Lake Forest College. He began his career in 1882 at the Holt-Balcom Lumber Company in Chicago, where his father was a partner. In 1888 he moved to Oconto, Wisconsin, where there was also a branch of the lumber company, and began work there, eventually serving as president.
Holt also served as president of the Oconto Canning Company, the Oconto River Improvement Company and the Holt Hardwood Company, the latter of which he was also chairman of the board. Additionally, he was director for a time of the Oconto Falls Manufacturing Company. Holt helped found the Northern Hemlock and Hardwood Manufacturers' Association and the National Lumber Manufacturers’ Association.
Holt served as mayor of Oconto from 1904-1908.
Holt was married in 1895 to Lucy Rumsey Holt. The couple had four children, Jeanette, Alfred, Mary Eleanor and Donald.