Little is known about the black men and women who served as Union intelligence officers, other than the fact that some were former slaves or servants who escaped from their masters. Others were Northerners who volunteered to pose as slaves to spy on the Confederacy.

There are scant references to their contributions in historical records, mainly because Union spymasters destroyed documents to shield them from Confederate soldiers and sympathizers during the war and vengeful whites afterward.

Hari Jones, curator of the African American Civil War Museum in Washington, says many of these spies are unnamed and rarely receive glory.