Artistic interventions in “America’s Attic” indicate the region’s importance to the geographical, ethnic and cultural history of the American Southwest As the largest alpine valley in the world, Colorado’s San Luis Valley is a land of sand dunes, wetlands and farmland—nearly all of it above 8,000 feet in elevation and all within a footprint of roughly 150 by 75 miles. Only sparsely covered by historians and geoscientists, the San Luis Valley has been home to mixed Hispanic ancestral villages, Spanish and Anglo settlements, Indigenous territories, and Catholic, Mormon, Amish, Hindu and Buddhist communities. This publication summarizes M12 studio’s Landlines Initiative, a multiyear engagement with the San Luis Valley involving 18 artists, which took place from 2018 to 2022. M12 is a Colorado-based collaborative studio known for art projects that explore public space, rural cultures and landscapes. Of their most recent work, former United States Secretary of the Interior Ken Salazar says “ Landlines … underscores the imperative of preservation and telling the stories of the unique and wonderful history of the San Luis Valley.”