EDXRF analysis of an obsidian scraper from the Spiro Mounds, Oklahoma, shows that the source material was from Pachuca, Hidalgo, Mexico. Given the distinctive peralkaline character of the obsidian, the source assignment is considered extremely secure. The artifact was recovered from the east tunnel of Craig Mound, Spiro, immediately after the cessation of commercial digging in 1935, and has been in the Smithsonian’s collections since 1937. Despite more than 150 years of speculation regarding supposed contact with and influence from the region, this represents the first documented example of Mesoamerican material from any Mississippian archaeological context in the Precolumbian southeastern United States.