The Grand Loop Road Historic District is a 140.14 mile road system which provides the primary visitor access to the major points of interest and visitor facilities in Yellowstone National Park. The current alignment of the Grand Loop Road grew from early wagon trails that followed river valleys and lakeshores. During the first 30 years of development, the road was in constant change, but by 1905 the interior road system connecting natural attractions, hotels, and entrance roads had crystallized into the present figure-eight configuration known as the Grand Loop Road. Having been built over many decades with many different standards, techniques, materials, and under many administrators, the Grand Loop Road retains basically the same configuration as it was first built, although some small sections have been abandoned or transformed into scenic roads.
The alignment is the way in which the road moves across the landscape; the curves, straight sections, and roadway movement to the left or right constitute the horizontal alignment; the movement of the roadway up and down hills being the vertical alignment. Although changes have been made to improve the road and to meet weather, natural, and geologic concerns, it is the continuation of the philosophy of design that harmonizes the road with the environment that is important. The Grand Loop Road retains elements of grace in alignment with features constructed of natural materials to a scale compatible with the natural environment, and the roadside vegetation contribute to the natural setting, evoking a feeling of distinction that differentiates it from modern roads. Landscape details such as stone curbing at pullouts, masonry culvert headwalls, guardwalls, retaining walls, and log railing were added to continue the design philosophy of using natural materials.