Frank McGuire (McGuire-486) was said to have run away and joined the Union army during the Civil War. I have found two Francis McGuires who enlisted in the 14th Brooklyn (84th NY Infantry Reg't). Both were 18. It was said that Frank (obviously) lied about his age. One of the McGuires deserted while the unit was stationed on Hart Island in NYC. This sounds like a lonely 13-14 year old kid running home to mommy when he was close enough to do so.
Any hints on how to narrow this down some?