Chapter boundaries are taken from the official Ninety-Nines Chapter & Section map saved September 4, 2026. U.S. ZIP coordinates and Canadian forward sortation area (the first three characters of the postal code) coordinates are retrieved at lookup time from the public Zippopotam.us service. If a U.S. ZIP centroid is outside all official chapter polygons, the tool assigns the closest chapter territory. Canadian postal codes are routed using current Canadian chapter service areas and nearest-chapter geography.