Treelines can serve as model ecotones in their response to climate change. However, the role of tree architecture at treelines is poorly understood. This paper examines tree architectures at a fast-migrating diffuse treeline in a bowl on the western slope of Pikes Peak (Colorado). Investigating the spatial distribution of the allometric types, the relationship between the growth rate and height for each architecture type, and the impacts of the changing climate on the architectural spatial distribution. The study site was divided into an Upper Zone (UZ) and Lower Zone (LZ). We found multiple distinct architectures within this diffuse treeline. Unexpectedly, tree architectures did not follow a spatial distribution pattern of clustering or avoiding with like and or different architectures. Krummholz and Cone architectures were found growing in close proximity to one another, signifying that the upper climatic boundary at this site has advanced up in elevation. These multiple architectures are able to represent current and past climatic conditions. Advancement is occurring at such rapid rates that tree established architectures are not able to release from their path dependency. To my knowledge, this is the first study that examines multiple tree architectural types within a treeline and how they are distributed in space.