Opened in 1899, the Saint Joseph Sanitarium and Bath House is the only building remaining from the Mount Clemens bath era. Beginning in 1870, people suffering from rheumatism, blood poisoning, diabetes and skin diseases, among other ailments, sought the curative powers of the baths. The city was hailed as "The Great Health & Pleasure Resort of Michigan." By 1911 the city boasted 78 hotels and 11 bath houses. Elegant and modern, Saint Joseph Sanitarium sported parlors, a library, steam heat, electric lighting, and a hydraulic elevator. It offered mineral baths until 1952.
In 1900 the Sisters of Charity of Mount Saint Joseph established a fifty-bed hospital in the Saint Joseph Sanitarium and Bath House, which they operated. That same year, the director, Sister Immaculata D'Arcambal, founded one of the first state-licensed nurse training programs here. Saint Joseph's eventually became the major hospital between Detroit and Port Huron. The present structure comprises the original Colonial Revival building, designed by local architect Theopholus Van Damme, and several additions. In 1990 Saint Joseph's was transferred to the Sisters of Mercy.