On the northwest edge of the city of Sheridan is Fort Mackenzie, a hospital administered by the Veterans Administration. The hospital is situated on approximately 272 acres of land, which is a small parcel compared to the 6, 280 acres that once was the Fort Mackenzie military reservation. Within that acreage are approximately seventy buildings and structures, most of which are arranged in two north-south rows and along a fishhook-shaped avenue. Two-thirds of the buildings within the hospital grounds were constructed in the first decade of the twentieth century when Fort Mackenzie was a military post. These buildings served various functions such as administrative offices, living quarters, hospital wards, warehouses, and maintenance shops. They are constructed of red brick in the colonial style. The rest of the hospital structures, built after 1930 and during the years the post served as a Veterans Hospital are complimentary in style and construction materials to original fort buildings. Fort Mackenzie was converted from a military post to a veterans hospital in the early 1920s.

Fort Mackenzie was named for Ranald Slidel Mackenzie (1840-1889), veteran of the Civil War and the Indian Wars of the West and Southwest. As colonel of the Fourth Cavalry, Mackenzie took part in the Powder River Expedition of 1876. In November of that year, leading a mounted column during General George Crook's winter campaign against High Plains Indians, he surprised and defeated Chief Dull Knife's band of Northern Cheyenne near the edge of the Big Horn Mountains. Fort Mackenzie was established as a military base for the purpose of protection of white settlers in a Rocky Mountain-High Plains region home to Indians belonging to half a dozen different tribes. In September, 1898 Charles F. Manderson, a former senator from Nebraska, and others, informed the War Department of the need for a military post in the Northwest and recommended Sheridan, Wyoming as a site. In October, 1898 General E. V. Sumner, Commander of the Department of the Colorado and the Missouri, was directed by the War Department to investigate and report upon the matter of establishing a military force at Sheridan. In his report Sumner supported Manderson's claims and on December 14, 1898, the Secretary of War approved the report and authorized the expenditure of $12,000 for temporary buildings at Sheridan. Legislation was introduced which called for the establishment of a post near Sheridan and included a $100,000 appropriation. The bill was signed by President McKinley on April 7, 1900. The garrison was at its peak strength with 601 men in 1911. Fort Mackenzie's usefulness as a military post was at an end with the entry of the United States in World War I in 1917. The post was officially abandoned on November 3, 1918.

The fort was transferred from the War Department to the Public Health Service in March 1921. A year later it was transferred from that agency to the Veterans Bureau. In March 1922 President Harding signed a deficiency appropriation bill containing an item of $100,000 for use in converting the post to a hospital, and that spring the first patients began to arrive at Fort Mackenzie Veterans Hospital. When the hospital opened it had a bed capacity of 125 patients. At peak patient load just after World War II, the hospital contained 900 patients and was one of the largest neurophychiatric hospitals in the country. At the time of its nomination to the National Register of Historic Places, the hospital had an operating bed capacity of 364, a staff of 505 and a budget of $10,000,000.

The significance of Fort Mackenzie as a historic site derives from both its history and its architecture. Its history relates to two major functions: its function as a military post and as a veterans hospital. From 1898 to 1916 Fort Mackenzie was an army post, but it is not clearly understood what role it played in American military history. That it had an active role in the High Plains Indian Wars is doubtful, since fighting had ceased and Indians were located on reservations two decades before the post was established. Wyoming's congressional delegation tried to establish it as a regimental post, but that effort was likely inspired more by economic and political, rather than military reasons. The existence of the many buildings and structures at Fort Mackenzie affords physical evidence of the impact the fort has had upon the lives of those associated with the facility. The dozens of red-brick colonial style buildings form an impressive complex that is equaled or surpassed only by F. E. Warren Air Force Base in Cheyenne and Fort Yellowstone at Mammoth, as a homogeneous collection of historic federal buildings in the state.

Holy Name Catholic School is one of the oldest Catholic schools in Wyoming, and the oldest Catholic school building in the state. Holy Name has provided education to Catholic and non-Catholic students in Sheridan for almost 100 years, making a significant contribution to education in the community. The 1914 school building is one of the oldest remaining school buildings in the state, and the second oldest school building in the state still being used as a school. It represents a trend in early 20th century grade school design which combined elements of the Prairie and Craftsman styles with the more common Classical Revival to give the school a welcoming and homelike appearance appropriate for young children. The 1952 addition was typical of the many school buildings constructed in Wyoming after World War II, with its hint of the International style in horizontal emphasis, flat roof, minimal ornamentation and bands of large windows.

Mount View (the Brooks-Yonkee House) was built in 1911-1912 for Lyman Herbert Brooks, a prominent Sheridan businessman and politician. It was designed by architect Glenn Charles McAlister of Billings, Montana and represents the Prairie School style of architecture. West of the main house is the carriage house in which the Brooks family lived during construction of their home, and later was used for the Brooks' horses and carriages.

Mount View is significant for its association with Lyman Brooks. Brooks pursued a variety of commercial interests including cattle ranching, hardware, lumber, banking, and real estate. He was also active in civic and social endeavors and served in the Wyoming State House of Representatives and on the Board of Trustees for the University of Wyoming. He was among a small group of entrepreneurs who helped shape the early economic growth of the city of Sheridan. The house is also significant as an outstanding example of Prairie School architecture and as a work of a master architect, Glenn McAlister. McAlister designed a number of important buildings in Montana and Wyoming.

The Robinson-Smith House was built in 1909 and is a remarkably well preserved example of an American Foursquare house. The American Foursquare form was popular from the mid-1890s to the 1930s and was a reaction to the ornate elements of the Victorian period. It was designed by locally renowned architect Glenn C. McAlister. Other notable properties designed by McAlister include the Sheridan County Courthouse, Mount View, and Trail End. The house was the home of William N. Robinson, his sister Rebecca, and her husband Atley Smith. William Robinson was an early pioneer and rancher in Sheridan County and was one of Sheridan County’s first County Commissioners serving three terms in office.

The Sheridan County Courthouse was constructed in 1904-1905 with elements of two architectural styles, Neo-Classical Revival and Beaux Arts. Architecturally, the Courthouse is one of the most imposing courthouses in Wyoming and one of the most monumental government buildings in the state, outside of the Capital City of Cheyenne. The Courthouse exemplified the trend in Wyoming, at the turn of the century, toward construction of stately government buildings that were impressive and authoritative in character. Built during a boom period in Northern Wyoming's history, the Courthouse symbolizes the determination of the people of Sheridan County to achieve an element of permanence. Located on the southwest corner of the courthouse complex, the sheriff's office-jail was constructed in 1913. The jail affirmed that the citizens of Sheridan County would remain a continuing, positive force in the history of Wyoming and became an integral part of the Courthouse Square.

The Sheridan County Fairgrounds Historic District is part of the 40 acre fairgrounds tract. The district consists of the 1923 brick Exhibit Hall, three circa 1939 Works Progress Administration (WPA) constructed sandstone buildings, a 1930s frame barn, and the 1950 frame horse stalls. A dedicated fairgrounds was constructed in the county by the late 1880s, then moved to its current site in 1906. The Sheridan Wyo Rodeo began in 1931 and it, along with the county fair, became two of the most anticipated annual events for county residents. The Sheridan County Fairgrounds Historic District serves as a vital link to the county’s agricultural and western roots. Three of the buildings were constructed by the WPA. The iconic pavilion is an excellent example of the stone work that was associated with WPA and New Deal construction.

The Sheridan Flouring Mills, Incorporated was originally constructed by J. W. Denio in 1920-21. It is an elongated rectangular reinforced concrete building with a two-story south wing, a central six-story segment, and a two-story brick element on the north end. These components represented the milling, packaging, and storage portion of the flour mill. There is a narrow intervening open space between the north end of the building and a reinforced concrete grain elevator and smokestack and seven pairs of attached grain storage tanks. In 1978 the mill was converted to a motel, which is now known as the Mill Inn. The south side of the elevator still bears a multi-colored logo with a cowboy on a bucking bronco and mountains in the background. The sign reads ''Best Out West Enriched Flour, Tomahawk Feeds For Livestock and Poultry, Sheridan Flouring Mills Inc.''

The Sheridan Flouring Mills, Inc. represents one of the most important early commercial enterprises in the City of Sheridan and Sheridan County. It served not only Sheridan but also the surrounding agricultural region including southeastern Montana and northeastern Wyoming through its network of farmers and grain elevators located along the mainline of the Chicago, Burlington and Quincy Railroad. It encouraged the growth of different strains of wheat by local farmers and provided a reliable market for their crops. It also converted these raw materials into flour, livestock feed, and other products to service the demands of the local community, as well as a much larger national market that extended from coast to coast. It became one of Sheridan's largest and most enduring employers with a substantial payroll and was also one of the largest taxpayers in Sheridan County and in the State of Wyoming. It provided a substantial income for the hundreds of farmers in the region who depended upon the mill as a buyer for their agricultural products. At this location, the Sheridan Flouring Mills, Inc. served Sheridan and the surrounding region from 1921 until finally closing in 1972.

Located on Main Street between Burkitt and Mandel Streets, the Sheridan Main Street Historic District comprises architecturally and historically significant buildings dating from the late 19th century to the early 20th century, with the majority of its buildings constructed in the 1910 and 1920 periods. Mixed elements from different classical styles are characteristic of the architecture. Sheridan was platted as a town by John D. Loucks in 1882. Loucks was said to have platted the town on the back of a sheet of wrapping paper by the tallow of a candle. Once the town was platted, it was then approved and incorporated in 1884. By the end of 1884, most of the lots of the original forty acre plat of the Sheridan townsite were occupied. As the Main Street Historic District was part of the ''original town'' and the survey maps still list the southern part of Main Street as ''original town,'' one can easily see that Main Street grew to the north as the town increased in population. In 1890 Sheridan had a population of 281 and by 1900 there had been a 455% increase to 1559 with the coming of the railroad, the opening of many coal mines in the vicinity of Sheridan, the arrival of townspeople, and the settling of ranchlands. By 1907 the City of Sheridan had a population of 4927. Sheridan as a business community was thriving during the first twenty years of the 20th century and Main Street was the center for trade, commerce, and government for the city and the county.

St. Peter’s Episcopal Church is one of the few historic churches remaining in Sheridan designed in the Gothic Revival style. The building was completed in 1912 with additions built in 1958. The original portion of the building was designed by architect Edward Ellsworth Hendrickson of the Frank Miles Day firm in Philadelphia. The building features a stone foundation, arched stained-glass windows, engaged buttresses, parapet walls, and a grand tower. The interior is characterized by dark-stained woodwork, decorative beams with carved dentils, and original oak pews. Stained-glass windows designed by the prominent Charles Connick Studio of Boston were added beginning in 1958. Connick was a well-known and prolific designer of stained-glass, however, St. Peter’s is one of only three churches in the State of Wyoming known to contain windows produced in his studio.

From the time the home was started in 1908, and July 16, 1913, when it was ready for occupancy, John B. Kendrick was on the fringe of a political career which took him to the Governor's office in 1914, and to the U.S. Senate in 1917. Trail End, which was built at a cost estimated at $160,000 including major furnishings, became a summer home due to Kendrick's political success. The architect for Trail End was William MacAlister of Billings, Montana, and the interior designer was another architect, D. Everett Waid of New York City. Good workmanship and the best materials were employed from foundation to roof and the result is a blending of beauty and sturdiness. The foundation is built of Indian limestone but everything above is brick, laid in a difficult old Flemish bond pattern. A dark mahogany woodwork is an interior feature, and 36 box cars of it were shipped from Grand Rapids, Michigan. The tile and marble throughout the house was made to order by a firm in Omaha, Nebraska. Ceilings and walls of the home not covered by paneling were covered with canvas and hand painted by a New York artist. The home is an outstanding example of many other homes built between 1880 and 1910 by cattlemen in the developing towns and cities of the high plains and mountain states. Today Trail End is a State Historic Site.