Automated Postal Center - Gunpowder 4405 Austin Rd Gunpowder, MD 21010 Phone : (410) 676-1905 Business Category Automated Postal Centers Toll-Free           (800) ASK-USPS Post Office - Gunpowder 4405 Austin Rd Gunpowder, MD 21010 Phone : (410) 676-1905 Business Category Post Offices Toll-Free           (800) ASK-USPS United States Government--postal Service Us Gunpowder, MD 21010 Phone : (410) 676-1905 Business Category Government Offices-Federal Government Offices & Public Schools