During 1937, Isle Royale National Park received two surplus United States Coast Guard cutters and their two-man crews. They were designated NPS-1 and NPS-2. After a short time, the numbers led to some confusion and the ships were renamed. NPS-2 became the Beaver and NPS-1 became the first Ranger. From 1937 until 1942 these 75 foot wooden hull vessels were the workhorses for Isle Royale National Park. They carried Civilian Conservation Corps crews, building materials, food and other supplies. During World War II, many changes occurred throughout the National Park System. Changes were felt at Isle Royale when the Beaver was returned to military service and the Ranger remained at Isle Royale. Deprived of maintenance funds during the war, the wooden hull Ranger started to deteriorate. After World War II, the decaying Ranger was taken out of service and replaced by a surplus Army Minelayer. This 114 foot wood ship spent World War II defending American harbors. Now it would be known as the Ranger II. From 1946 to 1958 the Ranger II served most of the needs of Isle Royale National Park carrying up to 16 passengers and tons of cargo to the developing park.
During the Eisenhower Administration, a program was initiated nationwide to rejuvenate National Park lands and its facilities. Under this "Mission 66" program, Isle Royale asked for and received a new ship, the Ranger III. Today, the island is serviced by the Ranger III, the largest vessel owned and operated by the National Park Service. In 1958, the Christy Corporation of Sturgeon Bay, Wisconsin, built the Ranger III at a cost of 1.16 million dollars. Custom built for service to Isle Royale National Park, the Ranger III was a dream come true for park management, tourism promoters and park visitors.