Four Cleveland physicians founded the Cleveland Clinic Foundation in February 1921, creating an institution dedicated not only to medical care, but also to research, innovation, and physician education. Three of the four founders had served together in a U.S. Army medical unit in France during World War I. The Cleveland Clinic Disaster of 1929 – a basement fire caused by combustible X-ray film that left 123 dead – was a tragedy that temporarily set back the hospital's progress. After World War II, however, the Cleveland Clinic rose to become one of the nation's leading medical centers.
During the 1940s and 1950s, Clinic researchers pioneered dialysis and kidney treatment and were the first to identify carpal tunnel syndrome and isolate the neurotransmitter serotonin. The Cleveland Clinic also emerged as a national leader in cardiac procedures. Clinic physicians performed the first coronary angiography in 1958 and continued to make significant advances in heart surgery techniques in the proceeding decades. The Clinic's main campus, located along Euclid Avenue in Cleveland's Fairfax neighborhood, has undergone tremendous growth since the 1970s. As adjacent land has been purchased and numerous new facilities constructed in a process of expansion, it is no great surprise that the Cleveland Clinic has become one of the city's largest private employers.