Longmont Sister Cities Association Share: NonprofitNonprofit Longmont Sister Cities Association Visit Website Request Info P.O. Box 2216 Longmont, CO 80502 720-352-6774 longmontsistercities.com About Map About Strengthen connections within our own community and through the world community with educational & leadership opportunities,being an information resourceand a communication conduit to the international community and Sponsoring What's Nearby? Distance: 5 10 15 20 25 50 mi.