The park grounds abutted Fort Mackinac, which continued to serve as a garrison of the United States Army during the operation of the park, as well as island geological features such as Arch Rock and Sugar Loaf. The fort's commander ran the park and federal troops served as park rangers, as at Yellowstone. The park had the authority to construct roads and trails and to lease small numbers of lots for buildings to offset its expenses as no federal money was provided to run the park. The park lands had to be available to the army for military training and in time of war.