Springs Historic District. Facilities Fort Yellowstone was constructed between 1891 and 1913 on the eastern edge of the Mammoth Hot Springs terraces, southeast of the present Mammoth Hotel, at a cost of approximately $700,000 ($16 million in 2013 dollars). By 1905, three more troops of cavalry had been added to the original Company M contingent of 50 soldiers, and during this period the fort facilities were almost continuously expanded to meet the requirements of park administration, ordinary cavalry training, and growing numbers of visitors. The initial wave of construction between 1891–97 was representative of typical army posts of the period. Like other western military posts, the earliest buildings erected at Fort Yellowstone were constructed according to quartermaster general standardized plans. In design, they were of a generally spartan appearance with a few Colonial Revival style domestic elements, described by the army as "cottage style". The buildings were of one to two-and-a-half stories in height, and of frame construction with drop siding and stone foundations, with evenly spaced double-hung sash windows and prominent porches. A second phase of building and upgrades started in 1908 which resulted in the prominent architecture visible at Fort Yellowstone in the 21st century. Built from locally quarried sandstone, these buildings defined Fort Yellowstone. The most prominent of the structures built in the later period is the Horace Albright Visitor Center which was originally the bachelor officers' quarters (Bldg 1). Each historic building in the fort and the park was assigned an official number, with the original bachelor officers' quarters being building number 1. Architects Reed and Stem and Robert Reamer along with the U.S. Army Office of the Chief Quartermaster, Department of Dakota participated in the design of many of the facilities. Engineer facilities and landscaping were designed by Captain Hiram M. Chittenden of the U.S. Corps of Engineers. Initial construction period 1891–1907 The first building constructed at Fort Yellowstone was the guardhouse (Bldg 9) at the southwest corner of the fort. In 1891, visitors traveled the lower Mammoth road through what is now the main residential area for park personnel. The guardhouse was the first building they encountered in the Mammoth area and there was always a sentry on duty to check visitors entering the park. The building is now a private residence. The original fort administration building (Bldg 8) was located immediately next to the guardhouse and is now also a private residence. Of