A converted two-story house served as the county hospital in 1907, a year before the Chicago, Milwaukee, St. Paul and Pacific Railroad arrived in Miles City. With encouragement from the railroad, which needed a place to treat injured workers, the county decided to build a larger facility. The architectural firm of Link and Haire designed the thirty-five-bed hospital circa 1910. The building's trussed porticos reflect the era's popular Craftsman style. Its hipped roof and distinctive curvilinear parapet evoke the Mission style. Inspired by the Spanish missions, which were an important source of medical care in the early Southwest, the style was a popular choice for hospitals. Other Mission style hospital buildings include ones built in Helena and Missoula during the same era. The Presentation Sisters of Aberdeen, South Dakota, assumed management of the hospital shortly after its completion. Originally a teaching order, the Presentation Sisters entered nursing after a 1900 diphtheria epidemic, establishing hospitals in Aberdeen, Mitchell, and Sioux Falls, South Dakota, as well as in Miles City. As did other Presentation hospitals, Holy Rosary offered a nursing certificate within a year of its opening. The 1918 influenza epidemic increased support for the hospital, allowing the sisters, who had purchased the building from the county in 1919, to expand their operation. Link and Haire designed the compatible, flat-roofed annex. Built in 1922, it boasted modern medical and surgical units and increased the number of available beds to eighty-five. The Presentation Sisters managed the hospital through drought, depression, and war, before constructing a new hospital in 1948.