Participants representing Union troops take part in the 149th Gettysburg Re-enactment on the site of the battlefield in Pennsylvania. Photos: Corbis; Cliff Carter; William B. Radell; Michael J. McAfee, senior editor of Military Images

Irving Moy (centre) re-enacts the role of Guangzhou-born Joseph Pierce during an event at Fort Trumbull State Park in New London, Connecticut.

Irving Moy, dressed as Joseph Pierce, at the latter's gravesite in Meriden, Connecticut.

The tombstone of Hong Kong-born Thomas Sylvanus in Oakland.

An amputation being carried out during the Battle of Gettysburg in July 1863.

Bodies of soldiers killed at Little Round Top, the site of an unsuccessful assault by the Confederates against Union troops on July 2, 1863.