Dinwiddie took some courses at Columbia University (1881–1883); and then he worked as a customs inspector in Corpus Christi, Texas (1883–1886). He worked for the Bureau of American Ethnology (1886–1895); and then he decided to change careers, becoming a foreign correspondent and photographer.
William Dinwiddie was twice married. In 1891 he married Mary E Towers, daughter of Chatham Moore Towers and Sallie Lewis Nuckolls. They were the parents of two children: Dorothy and Redfield Towers Dinwiddie. In 1901 he married Caroline Miller Brooke, daughter of William S Brooke and Mary Shoemaker Hallowell.
- War Sketches in Truth
- Our New Possessions
- The War in the Philippines
- The War in South Africa
- Haverstock, Nathan A. (1996). Fifty Years at the Front: The Life of War Correspondent Frederick Palmer. Washington, D.C.: Brassey's. ISBN 978-1-57488-040-3; OCLC 33041795
- Leonard, John William and Albert Nelson Marquis. (1899). Who's who in America. Chicago: A. N. Marquis. OCLC 35908327
- Roth, Mitchel P. and James Stuart Olson. (1997). Historical Dictionary of War Journalism. Westport, Connecticut: Greenwood Publishing Group. ISBN 978-0-313-29171-5
- The Charleston Gazette. Jun 18, 1934. Charleston, West Virginia. Page 2, column 3. "William Dinwiddie, Newspaperman, Dies"