1863 William Worrall Mayo arrives in Rochester 1883 Tornado leads to building of St. Marys Hospital 1892 Mayo brothers (Will and Charlie) invite others to join family practice • 1905 Frozen section for surgical diagnosis • 1907 Unified medical record • 1919 Mayo brothers place assets in Foundation • 1939 Mayo brothers die • 1950 Nobel prize for cortisone • 1955 Mayo team pioneers heart surgery with perfected bypass machine