Casgrain was surgeon for the local militia during the Fenian raids. He served as a member of the town council for Windsor and as a long-time member of the local school board. He was named a knight of the Order of the Holy Sepulchre by Pope Leo XIII in 1884.
Casgrain served as a medical officer for the local militia during the Fenian rebellions. He was also a member of the town council in Windsor and had been involved with the local school system for many years. In 1884, he received a prestigious award from Pope Leo XIII by being knighted as a member of the Order of the Holy Sepulchre.