John McClay married Mary Jane Gamble on Dec. 31, 1860, in Eden Prairie. Their two sons, James and John, were born in Eden Prairie.

John McClay volunteered for the Civil War and received a $300-bounty for enlisting. His brother Samuel McClay was already a Second Lieutenant in the service.

After the Battle of Gettysburg, the Minnesota 1st Regiment received a special unit thank you at the U.S. Capitol and the whole Regiment was sent back to Minnesota to muster out, arriving Feb. 15, 1864. The 1st Minnesota then reestablished at Fort Snelling, with volunteers from the original 1st Regiment and new recruits. John McClay became part of that Regiment. He was mustered into service at the age of 24 and became a private in Company I.

In May 1864, the 1st Battalion went back to the east coast to fight along with General Grant's troops. They also fought a number of secondary actions (skirmishes) near Petersburg, Va. and one of those was at Deep Bottom, Va.

During the battle, John was seen to fall mortally wounded in the abdomen in the first charge in Deep Bottom, Va., on Aug. 14, 1864. Men who saw him fall wounded were told that he had been placed on a boat for removal to a hospital in Washington, D.C. It is believed he died on the transport boat and was probably buried on the shores of the Potomac, or buried at sea.

There is a Civil War memorial located at the Pioneers Cemetery on 104th and Lyndale in Bloomington which bears the names of John McClay and other Civil War Veterans and states that John McClay died in the service.