McGrath was born in 1920 in Carlstadt New Jersey, and in the 1940's after the invasion and the Japanese's bombed Pearl Harbor he volunteered and was drafted into the army and volunteered for paratrooper. he carried a Bazooka and also a M1 Carbine,
He was trained at Camp Taccoa under Captain Herbert M. Sobel, and later trained in Aldbourne England and he joined Easy Company at Fort Bragg.
McGrath did his first jump into Normandy on D-Day and he partook into Carentan, attack by an army of German Tiger Tanks, he and Lieutenant Harry Welsh together knocked out a Tiger Tank with McGrath's Bazooka, he was very frightened, he screamed "You're going to get me killed Lieutenant," but Welsh had to do his job, also he successfully destroyed the Tiger Tank and with 1st Lieutenant Winters and his men gave them covering fire-power and both Lt Harry Welsh, and McGrath made it to safety, and when the Sherman's Tanks arrived the men won the skirmish. After D-Day, McGrath was awarded the Silver Star and the Bronze Star Medal with clusters.
McGrath participated in Operation Market Garden in September 1944. He also fought in the Battle of the Bulge, but at the time he was with HQ platoon so he was slightly behind the line, McGrath also found Hilter's car, and tested if it was bulletproof, McGrath became one lucky soldier and never got hit and later partook in the battle of Foy and survived it, also went through other campaigns with Easy Company and survived to the rest of the war,
After the war he worked as a Truck Driver and as a volunteer firefighter, and served as fire chief from 1970 to 1971, and later as a fire inspector and Fire Official for the Borough of Elmwood Park, He was married to Irene (nee Blauvelt) McGrath for 64 years, they had two sons, John Jr. and James. McGrath attended many reunions before his death in 2012,