William Henry Carroll (1810 – May 3, 1868) was a wealthy planter, a postmaster, and a brigadier general in the Confederate States Army during the American Civil War.

The streets were filled with spies from both sides, exiled Confederates of high rank, sympathizers, arms dealers, Union detectives and saboteurs.

Carroll became a fixture at the luxurious St. Lawrence Hall on St. James Street (now Saint Jacques Street) which was where the more affluent Confederates in Canada stayed such as Jacob Thompson, Clement Claiborne Clay, James Westcott, Moses Montrose Pallen, Luke P. Blackburn, Nathaniel Beverly Tucker and even John Wilkes Booth.

On June 8, 1865, Carroll and a friend named O'Donnell confronted Sandford Conover in front of the William Ennis saloon.

They demanded to know whether he was using the alias James Watson Wallace, the man who had spun the web of false testimony towards the Assassination of Abraham Lincoln.