In contrast, the earliest church-run medieval hospitals served primarily as havens for the homeless, the destitute, and those with diseases regarded as hopeless. Most of these were general medical and surgical-care facilities. Half had fewer than 100 beds. Academic teaching hospitals, which are usually attached to medical schools and have internship and residency programs, accounted for about 10 percent of all hospitals. They were often larger institutions, controlling about 25 percent of the nation's hospital beds.
Hospitals operate under one of three types of ownership.
The federal government operates hospitals through the Veterans Administration, the Department of Defense, and the armed services as well as administering Public Health Services and Indian Health Service facilities, prison hospitals, and special institutions run by the Alcohol, Drug Abuse and Mental Health Administration. Every state operates one or more hospitals providing care for the mentally ill, the retarded, and tuberculosis patients. Nonprofit hospitals may be run by religious groups or associations of citizens. Since the mid-1970s, hospital chains have proliferated, often through buying or leasing financially pressed municipal or county facilities and university attached teaching hospitals. The chains have the capital to improve often rundown physical and technological facilities.