It is a truism that maps cannot exist without boundaries, whether those boundaries are the borders of the map itself or the geographic coordinates circumscribing the limits of the physical space being mapped. Grand Canyon National Park, like all national parks, has written and legislated descriptions that form the basis for mapping the evolving nature of the park. The year 1925 saw the first significant re-writing of the legal boundaries of Grand Canyon National Park since its legislative creation in 1919.  This presentation will discuss the “sausage-making” involved in re-writing the borders of Grand Canyon National Park.