His father was state's attorney, deputy collector at the Port of Baltimore, and veteran of the Civil War.
Dallam's maternal grandfather was Israel D. Maulsby, state delegate of Harford County.
[4] He attended Bel Air Academy and graduated from the University of Maryland School of Law in 1888.
In 1896, he was appointed as Secretary of State of Maryland by Governor Lloyd Lowndes Jr.
[1][5] Dallam was president of the Harford County Mutual Fire Insurance Company from 1894 to 1939.