Upon commissioning, Mackinac was assigned to duty on the Great Lakes as a boarding boat at Erie, Pennsylvania.

When the Great Lakes iced over for the winter, she was placed out of service at Milwaukee, Wisconsin, on 1 December 1905 to await the opening of navigation in the spring of 1906.

When the United States Coast Guard was created in 1915 by the merger of the Revenue Cutter Service with the United States Lifesaving Service, Mackinac, redesignated USCGC Mackinac, became part of the new Coast Guard.

As USS Mackinac, she served in the Atlantic in the 3rd Naval District during the war, patrolling the United States East Coast.

She was stricken from the Naval Vessel Register and returned to the Coast Guard on 22 September 1919, once again becoming USCGC Mackinac.