The forty bridges in this thematic study are the best of their types which were still in use on the state and county road systems in Wyoming when the study was completed in 1982. Selected from a statewide survey of all functional vehicular trusses and arches using a specific evaluation criteria and methodology, most represent superlatives of their generic engineering types (i.e. truss configuration and connection types) while typifying bridgebuilding and transportation trends in the state. All were built in the first three decades of the twentieth century (1905-1935). Although bridges were put up during the earlier periods of overland wagon emigration, they had not begun to proliferate in the state of Wyoming until the early twentieth century with the emergence of the automobile as a principal form of transportation. All the listed bridges display a remarkable homogeneity of construction and operational histories. Generally, county-built trusses were contracted through competitive bidding among several Midwestern bridge erectors and built from standardized designs using prefabricated components. After creation of the Wyoming Highway Department in 1917, the role of the counties in truss bridge construction diminished. The later highway department bridges were typically designed from standard plans maintained by the department and built by local contractors from components fabricated in the same Midwestern foundries.

One feature that all steel truss bridges shared was their versatility. Quickly erected, they could also be dismantled and moved if necessary. Many county road bridges in Wyoming had begun service as railroad bridges, sold or given to the counties as obsolete structures. Similarly, early highway bridges which had become unsuitable to handle increasing volumes of traffic were sometimes replaced with new trusses, with the older bridges demoted to places along less traveled roads. After World War II, new trussbuilding was rare in Wyoming. Today trusses have been largely superseded by more sophisticated engineering designs and are seldom erected. The remaining highway and roadway truss bridges are remnants of past technologies, whose numbers are continually dwindling through attrition.

The Diamond Ranch is located northeast of Chugwater on Richeau Creek. The historical and architectural significance of the Ranch sets it apart from any other ranch in the state of Wyoming. The owner architect, George D. Rainsford, is representative of the many eastern and foreign stockgrowers who came west in the late 1870s to invest their fortunes in the high plains cattle industry. Rainsford was also unique in this group because of his simultaneous architectural contributions both at his own ranch and for his 1880's designs in the city of Cheyenne. In addition, Rainsford set the standard for fine horsebreeding not only in Wyoming but on an international scale, a factor which still influences Wyoming's horse ranching industry. The native stone buildings were utilized as part of a large family owned stock ranch. All buildings are constructed of rock face native stone with simplified ornamentation, a Rainsford trademark.

The Duncan Grant Ranch and its surrounding landscape are representative of ranching in the early era of Wyoming history. Duncan Grant immigrated to the United States from Scotland and homesteaded along the Sybille Creek in 1874. The family established the ranch in a typical manner, expending most time and energy on the ranch operations and less time of the house. They constructed a small two room cabin, irrigated the land via the Two Bar Ditch and built the barn and corrals. The Grant family ran approximately 400 head of cattle during this time. Duncan Grant also served as a foreman for the extensive Swan Land and Cattle Company. With this increased income the family undertook an extensive building project ca. 1890. This included a new house, ice house, bunkhouse, and an expansion of the barn.

Lake Guernsey State Park developed during the early 1930s on federal land that had been purchased for the North Platte River Project by the Bureau of Reclamation. The reservoir was first filled in 1927 following construction of the Guernsey Dam and Power Plant. The park, located near Guernsey in eastern Wyoming, features a lakeshore drive and a skyline drive, extensive original trails, and an exceptional group of Civilian Conservation Corps era buildings and features constructed of roughly worked local sandstones.

Worn from two to six feet into an eroded sandstone ridge located on the south side of the North Platte River about one-half mile south of the town of Guernsey, Wyoming, the Oregon Trail Ruts provide striking physical evidence of the route followed by thousands of Americans in their migration westward across the Plains between 1841 and 1869. The first recorded use of what was to become the Oregon Trail occurred in 1812, when Robert Stuart and six companions followed the route in returning to the East from Fort Astoria in Oregon. In the succeeding years, the route was used by numerous traders, trappers, and missionaries; but it was not until 1841 that the first wagon train, that of the Bartleson-Bidwell party, moved westward over the Trail. Over 100 emigrants followed the Trail west in 1842, and over 900, in 1843. In the ensuing years the numbers of emigrants steadily increased, and the Oregon Trail became a clearly defined and deeply rutted road across the country. With the completion of the Union Pacific Railroad in 1869, use of the Trail as an overland route to the Pacific rapidly declined, although sections of it continued to be used locally for many years. The combined effects of wagon wheel wear and cutting to ease passage over a rough place in the road, these ruts near Guernsey are probably the most prominent along the Oregon Trail and are unsurpassed in their clarity and integrity.

The Patten Creek Site (48PL68) is a prehistoric lithic procurement and workshop area located in the Hartville Uplift area north of Guernsey, Wyoming.. The predominant materials are Hartville (''Spanish Diggings'') Chert and small quantities of Hartville Quartzite. The site is a multiple component site with buried materials at least as deep as 3.6 meters. Early work indicates that Plains Archaic components are the most abundantly represented in the central portion of the site, but other components have been recorded as well. The site was first formally reported by the Smithsonian River Basin Survey for Glendo Reservoir as 48PL32, and later investigated more extensively in loose association with the Hell Gap Project of Harvard University. Excavations at the site were begun by Irwin and Irwin-Williams in 1960, and by Keller from 1963 through 1965. A minor Late Prehistoric component was recovered at Patten Creek, and it was speculated that quality lithic sources may have been locally exhausted by that time. Three distinct Plains Archaic components were identified which correspond roughly to the Early, Middle and Late Archaic. A single Frederick point was reported from the site, but the presence or absence of buried Paleoindian components at Patten Creek has not been demonstrated.

Constructed in 1917, the two-story, brick and stone masonry courthouse is eligible because it represents the early twentieth-century political growth of Platte County, which was created in 1911. The courthouse is also an outstanding example of early twentieth-century Neo-Classical Revival architecture in a public building. The functions for the Platte County Courthouse have remained the same for the past ninety years, documenting the activities of its citizens, establishing a permanent record of births and deaths, marriages, divorces and adoptions, real estate and vehicle records, probate and court records, election and business conducted by county commissions. As such, the courthouse acts as an archive for the history of the Platte County and represents a symbol of the sense of community and permanence for it citizens. The building also serves as an important gathering place for the numerous public activities required of its citizens.

The Powars II site, located in Platte County, Wyoming, is the only prehistoric hematite (red ocher) quarry thus far identified in the American archaeological record. The site is comprised of a hematite quarry feature and associated tailings containing an estimated hundreds of thousands of chipped stone, bone, and antler artifacts deposited during quarrying activities between ca. 13,000 and 11,000 years ago. The site certainly fulfilled a need for hematite; it contains digging tools and intact quarry features. However, Powars II also appears to have been a place where Paleoindians lingered to repair equipment and produce new stone tools over repeated occupations spanning 1,000 to 2,000 years. Prolonged use of Powars II created one of the largest assemblages of Paleoindian artifacts thus far discovered in North America — an assemblage that includes artifacts of the Clovis, Plainview/Goshen, Folsom/Midland, Agate Basin, and Hell Gap cultural complexes. Powars II has been disturbed in several ways, but it retains deeply buried in situ sediments that reflect site activities during its use. The Powars II site is one of the richest repositories of Paleoindian artifacts and in the Americas and investigations up until this point have just begun to understand the varied behaviors that formed this site over 11,000 years ago. The site has great potential to inform Paleoindian research for many years to come and is eligible for listing in the National Register of Historic Places at the national level of significance under Criterion D.

Register Cliff consists of a soft, chalky, limestone precipice rising over 100 feet above the valley floor of the North Platte River. The horizontal features of the cliff were created thousands of years ago by the erosive action of the river waters cutting through layers of soft sedimentary deposits. Register Cliff is a link to the romantic era of overland migration in Western America. It was an important mid-19th century landmark along the route of travel to Oregon and California and a place where countless emigrants inscribed names, dates, origins and messages in the soft limestone cliff faces. Although inscriptions are found at numerous places along the trail, Register Cliff represents one of the three best known ''registers of the desert'' -- the other two being Independence Rock and Names Hill.

Register Cliff was the first night camp west after leaving Fort Laramie. Under the shadow of the chalky bluffs on the south bank of the Platte River the emigrants paused to set up camp, to pasture their animals, and to rest and recoup from the hardships of trail travel. This stopover gave the wayfarers time to record the names and dates which have now become an enduring aspect of an historic era. Many of the names and dates at Register Cliff relate to the peak years of travel along the trail during the 1840's and 1850's. Several states are well-represented in the carvings with Ohio seemingly in the majority. It is likely that the cliff and its surroundings were a familiar stopping place during the fur trade era but inscriptions dating to this period that may have existed at one time have apparently weathered away. The earliest known date reads: ''1829 This July 14'', perhaps placed there by some French trapper or explorer to commemorate Bastille Day. One unusual series of names, representing three generations of Register Cliff scribes, are those of T.H. Unthank dated 1850, O.N. Unthank, 1869, and O.A. Unthank, 1931.

Charles A. Guernsey, a pioneer cattleman after whom the town of Guernsey, Wyoming is named, established his ranch buildings a short distance from Register Cliff in the 1890's. Guernsey's successor to the ranch, Henry Frederick, donated the site to the State of Wyoming to be preserved as a memorial to the spirit and accomplishments of the pioneers.

The Grant Ranch is situated north of Richeau Creek in the rolling hills of Platte County, Wyoming. Surrounding land is used for both grazing as well as the production of hay. Irrigation canals, reservoirs, as well as the creek provide water for farming purposes. The trees that surround the original buildings are cottonwoods, blue spruce and the vegetation is mature with large lilac bushes and native grasses. Corrals constructed from barbed wire and vertical log slabs are an integral part of the ranch. The buildings, structures, land and vegetation create a cultural landscape which was started in 1890 and is still used in the same manner over 100 years later. The Grant Ranch is an interesting mixture of hand crafted vernacular buildings along with buildings that were moved in and modern buildings that help maintain the economic vitality of the ranch. Within the ranch's historic district there are a variety of buildings as well as structures such as an irrigation ditch, the remnants of a lime kiln, and a dipping vat. The district also contains a small family cemetery.

The Grant Ranch is a representative Wyoming ranch which was established by Scottish immigrants in 1891. At the time the Grant Ranch was started on 160 acres of land, ranching in Wyoming had begun to change from large herds grazed on the open-range to smaller herds of cattle grazed on both public and private land. The founder of the ranch, Robert Grant, used his expertise from working in coal mines in Scotland, where he built drifts and supports, to construct very solid buildings at his ranch. He constructed an eight room stone house, a barn and other out buildings. Grant used skills he learned in Scotland to create lime in his lime kiln. The house, outhouse, barn and even the chicken coop were constructed with limestone and mortar made from Grant's own lime kiln.

Robert Grant joined relatives and friends who settled around Chugwater and what later became Slater. He was not one of the wealthy Scottish investors who came to the West to enlarge his holdings but instead was a man of modest means who used local materials to create his ranch. Grant slowly enlarged his holdings in what was Laramie County but eventually became Platte County. He and his wife Margaret helped expand the ranch by filing on land using among other legislation, the Desert Land and Homestead Acts. When Slater was no longer viable as a agricultural support community, the Slater Bank Building was moved for reuse to the Grant Ranch. The Grant Ranch is still in operation by the Grant family.

1917 Photo of Grant Ranch on file at the State Historic Preservation Office

The Sunrise Mine Historic District encompasses 225 acres in the rural, high desert foothills of eastern Wyoming, where the Sunrise Iron Ore Mine and company town operated from 1898 to 1980. The now abandoned town of Sunrise, Wyoming, where the mining operations and company town were located, lies on the floor of Eureka Canyon, surrounded by canyon walls on the north, south, and east. The soil in the district is red, due to the large amount of red ochre that accompanies the iron and copper deposits scattered throughout the area.

The property contains buildings, foundations and landscape features representing 80 years of iron-ore mining, with an associated company town. The district is a part of the Hartville Uplift, an area in southeastern Wyoming that connects the southern Black Hills with the Laramie Range. The Sunrise Mine was the principal source of iron used at the Colorado Fuel and Iron plant in Pueblo, Colorado, from 1899 until 1980, making it an important contributor to the economy of Colorado as well as Wyoming. Also, the Sunrise Mine was important in the social and ethnic history of the region. The unskilled workers at Sunrise included Italians, Greeks, Syrio-Lebanese, Japanese, Scandinavians, and English.

The Swan Land and Cattle Company was one of the several well-known foreign stock companies which operated in the United States. Located near Chugwater in eastern Wyoming, it was one of the largest cattle companies in the country and operated for over 70 years. Organized in Scotland in 1883, with a capital of $3,000,000, the Swan Land and Cattle Company had over 113,00 head on the books when the severe winter of 1886-1887 struck, reducing the company's herd to about 57,000 in 1887. Following this hard winter, the company went into bankruptcy and reduced its inventory and capital, with its herd cut down to 40,000 in 1893. The company continued to operate until 1904 when it went into the sheep business. At the peak of the company's sheep business in 1911, it ran about 112,000 head. The company continued its operations until 1945 when it began liquidating.

The Wheatland Depot, constructed in 1895, is situated at the east end of Wheatland's original ''main street'', Gilchrist Avenue, at its junction with the tracks. The Depot consists of four rooms laid out in a row. The waiting room is on the north, the Station Master's office with bay window next, then the express room for packages, ending with the large freight room on the south. The town of Wheatland and the neighboring farming district owe their existence to two events: the bringing of irrigation water through the Wheatland tunnel and the arrival of the railroad. Water made crops grow. The railroad made crops profitable. The Wheatland Depot was the point of arrival for most settlers and the point of departure for the area's products, sugar beets, wheat, cattle and produce. Until its closure in 1969, the Wheatland Depot was a focal point of commerce in the community.