This thesis examines past and current preservation techniques at Fort Union National Monument, New Mexico in light of increasing threats from climate change, inadequate stabilization practices, and diminishing agency resources, and aims to make recommendations for future preservation work at the site. Fort Union National Monument is the largest existing earthen ruin in North America and historically served as an active military fort and depot on the Santa Fe Trail between 1851-1891. The fort was abandoned in 1891, pillaged by locals for materials, and prior to the stabilization of the site in 1956, the adobe walls were left to weather and deteriorate into the abstract forms of former walls seen today. The deteriorative nature of earthen ruins, intended to be visited and interpreted by the public, pose particularly complex challenges for architectural conservators. Earthen sites are extremely vulnerable to moisture and their deterioration will be expedited in the case that there are missing drainage systems and structural features like roofs. Fort Union is no exception; it is a complex archaeological, architectural and cultural landscape, primarily of adobe construction, and founded on legislation that mandates it be preserved as a stabilized ruin. Preservation policy for the site was established in 1954 with the creation of the National Monument as a stabilized ruin without restoration or reconstruction. This preservation policy that restricts rehabilitation and reconstruction conflicts with traditional methods of preserving adobe. Since the 1950s, federal cultural resource management has been increasingly defined by resource type as represented in the creation of the National Park Service’s Cultural Resource Management Guidelines (NPS-28) however these guidelines are a challenge to apply to sites that do not fit perfectly into one category. This thesis proposes implementing current preservation practices at Fort Union according to a broader set of values as a complex archaeological, architectural and cultural landscape. Rethinking preservation practices can expand the interpretation and display of the site as well as preserve its original fabric.