Mayo Clinic was originally established in Rochester, Minn., at the close of the 19th century. Today, Mayo Clinic and its hospital campuses, Mayo Clinic Hospital, Saint Marys Campus, and Mayo Clinic Hospital, Methodist Campus, form one of the largest integrated medical centers in the world. Mayo facilities provide comprehensive diagnosis and treatment in virtually all medical and surgical specialties.

The clinical practice is the heart of the downtown Rochester. Also downtown are most of Mayo Clinic's clinical laboratories, research laboratories and its education activities, as well as Mayo Clinic Hospital, Methodist Campus, with its transplant programs in liver, kidney, pancreas, and blood and bone marrow. Located nearby, the Saint Marys Campus began in 1889, as a joint project between the Sisters of Saint Francis and the Mayo brothers and their father. (See history.)

Today, on its Saint Marys campus, Mayo Clinic services include a Level One Trauma Center, computer-assisted neurosurgery, and heart and lung transplant. Also located on the Saint Marys campus is the Mayo Clinic Psychiatry & Psychology Treatment Center, one of the largest psychiatric treatment groups in the United States, and Mayo Eugenio Litta Children's Hospital, with its pediatric and neonatal intensive care units.