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's involvement with the local militia during the Fenian uprisings, as well as his positions on the town council and school board, are notable aspects of his career. In 1884, he was honored by Pope Leo XIII for his service by being named a knight of the Order of the Holy Sepulchre.