Marcoux served in the militia during the defence of the town against the Americans in 1775-6. At the end of the American Revolution, he was placed on half pay and received a grant of land.
During the American Revolutionary War, Marcoux played a role as a member of the local militia that defended the town against the Americans in 1775-6. After the war, he was demobilized and awarded a plot of land as part of his post-war benefits.