Gosforth, Newcastle Upon Tyne born left back John Cooperthwaite began his football career after the First World War playing for Coxlodge in 1919, and had spells with both Carlisle United and Gosforth in 1920, from where he joined Third Division (North) club Ashington in August 1921, spending 1921-22 on their books without appearing for the first team. He played for Coxlodge British Legion in 1922 before joining Third Division (North) club Durham City on amateur forms in October 1922, making his Football League debut against Stalybridge City later the same month, and during his first three seasons at Kepier Haughs he made just a single appearance each season.
Still an amateur, he broke into City’s first eleven in December 1926 and played 26 matches during the remainder of the season, and made a further 13 appearances the next season, scoring 3 times in 5 matches as an auxiliary inside forward. However Durham City lost their League status at the season end, and Cooperthwaite re-joined Carlisle United in June 1928 having turned professional, where he scored both goals in his debut in a victory at Tranmere Rovers in February 1929 playing at inside left, and made two further appearances that season as a forward, before reverting to left back for both his first team matches for The Cumbrians in 1929-30. On leaving Brunton Park he joined Spennymoor United in 1930 before his eventual retirement.