To an expanding 19th century industrialist population, the network of Native American mounds in the St. Louis region were seen as ready fill material for the new railroads, towns, and building sites that facilitated new forms of capitalist growth. These mounds were artifacts that were celebrated and erased simultaneously—subject to curiosity and identity (St. Louis was known at the time as “Mound City”) but ultimately destroyed by the imperatives of industry and the human appraisals that gave these priority. Mounds were leveled. Factories were built. Roads and buildings were named after the mound features they replaced. This project is situated at the largest of these demolished mounds—the so-called “Big Mound” site—on what is now the north riverfont of St. Louis. The destruction of this mound was heavily documented and even resisted by certain civic groups at the time—but the photographic archive of un-building charts the gradual but uninterrupted erasure of this mound. On a two-sided billboard adjacent to the site, we have mounted two images: one from the 1870 un-building of Big Mound, and the other a present day photograph of an existing mound in the Cahokia State Historic Site across the river.