[1] Competing in four Summer Olympics,[2] he earned three bronze medals (Individual épée: 1928, Team foil: 1932, Team épée: 1932)[3] A native of Boston, Massachusetts, Calnan did not start fencing until he was a student at the United States Naval Academy in Annapolis, Maryland.

By the time he was a senior, he was captain of the Navy's fencing team.

Two years later, Calnan competed for the United States at the 1924 Summer Olympics in Paris where he finished tied for fifth in the team épée competition.

He was posthumously inducted in the US Fencing Hall of Fame in 1963, among the first inductees.

He is also the namesake of the George C. Calnan Memorial Trophy, which is given to the three-weapon championship team.