Leo Francis MacDonald was born on 20 December 1897, to parents George and Isabella (Leonard) MacDonald of Annandale, Prince Edward Island. He resided in Annandale with his parents and his five known siblings (Mary, Leonard, Victor, Louis, and George) until 1909, when the family moved to Cornwall, Prince Edward Island, to live on the family farm of his mother. Leo was educated at schools in both Annandale and Cornwall, until he began his formal education at Prince of Wales College and St. Dunstan's University by 1916.

For the majority of his life, Leo worked as a teacher, holding positions in both North River and Queens Square as early as 1916. He ended his teaching career in 1966 after an eight-year position as the first principal of Birchwood High School in Charlottetown, Prince Edward Island. In between his various teaching duties, Leo served with the Canadian Army. He trained for duty in the World War I, and although he did not see action, he would have had a great deal of knowledge about the experiences of those overseas as he was in regular correspondance with his brother, Victor, who was stationed in Europe during World War I. During the Second World War, Leo was assigned to serve overseas as the Lieutenant-Colonel of the No. 2 Company of the 6th Division Signal Corps. He was officially dicharged from the Canadian Army in October of 1946.

Leo married Helen Mary Towan in August of 1925, whereafter they resided in several locations around Charlottetown, including residences on Fitzroy and Hillsboro Streets. Leo and Helen had several children, many of whom died at either birth or infancy. Only one of their children, daughter Patricia, is known to have survived and to have had children of her own. As his pasttimes, Leo belonged to two well known societies on Prince Edward Island; the Knights of Columbus, and the St. Thomas Aquinas Society. Leo wrote and delivered speeches for both of these groups. Leo F. MacDonald died in retirement ca. 1968.