The origins of the state boundaries marked by the monument occurred just prior to, and during, the American Civil War, when the United States Congress acted to form governments in the area to combat the spread of slavery to the region. When the early territories were formed, their boundaries were designated along meridian and parallel lines. Beginning in the 1860s, these lines were surveyed and marked. These early surveys included some errors, but even so, the markers placed became the legal boundaries, superseding the written descriptions of geographical meridians and parallels. This includes the Four Corners Monument, which has been legally established as the corner of the four states.