Post Office - Humboldt 12814 E Main St Humboldt, AZ 86329 Phone : (928) 632-7411 Post Office - Humboldt Business Category Post Offices Toll-Free           (800) ASK-USPS Fax           (928) 632-5231 United States Government--post Office 12910 Main St Humboldt, AZ 86329 Phone : (928) 632-7411 United States Government--post Office Business Category Government Offices-Federal Post Offices Government Offices & Public Schools