Did Guatemala Sell Territory to Mexico? No

No historical evidence exists of Guatemala selling any territory to Mexico.

Both nations emerged from the Spanish Empire. Their border was defined by the 1882 Herrera-Mariscal Treaty (modified 1895), following arbitration by the U.S. (1897) and a 1902 convention. Disputes occurred (e.g., Chiapas/Soconusco region claimed by both early 19th c.), but resolved diplomatically—no sale.

Guatemala lost territory to Mexico only in the sense of failed claims (e.g., Belize, which Guatemala still claims partially), not via sale.