A native of Massachusetts, Stacy joined the Navy from that state and by January 15, 1866, was serving as a seaman on the USS Rhode Island.
On that day, while the Rhode Island was being resupplied in the harbor of Cap-Haïtien, Haiti, one of the crewman fell overboard.
The sailor was able to grab onto a rope but, due to a strong current, eventually lost his strength and let go.
[1] Stacy's official Medal of Honor citation reads: While coaling ship in the harbor of Cape Haiten, one of the crew of the Rhode Island fell overboard, and, after catching a rope, had been forced by exhaustion, to relinquish his hold.
Although the sea was running high at the time, Stacy, at the peril of his life, jumped overboard, secured the rope around his shipmate, and thus saved him from drowning.