Post Office - Gwinner 21 S Main St Gwinner, ND 58040 Phone : (701) 678-2679 Business Category Post Offices Toll-Free           (800) ASK-USPS Fax           (605) 357-4906 U S Government--postal Service, Post Office 10 N Main St Gwinner, ND 58040 Phone : (701) 678-2679 Business Category Post Offices Government Offices & Public Schools