Wheeler's regiment suffered heavy losses at the Battle of Gettysburg where he was killed in action at Rose Woods, near Devil's Den.

Wheeler and his regiment joined the III Corps and participated in the Peninsula Campaign and the second Battle of Bull Run.

At Bull Run, Wheeler, (now a major) temporarily assumed command of the regiment after Colonel William L. Brown was killed.

Due to heavy losses the entire III Corps was taken out of active duty during the Maryland Campaign to regain lost numbers.

At Gettysburg Wheeler was part of J. H. Hobart Ward's Brigade of David B. Birney's Division in the vicinity of Devil's Den and Rose Woods.