Post Office - Monroe 132 Maple St E Monroe, SD 57047 Phone : (605) 648-3210 Business Category Post Offices Toll-Free           (800) ASK-USPS United States Government--marion, Post Office Po Box 9998 Marion, SD 57043 Phone : (605) 648-3210 Business Category Government Offices-Federal Post Offices Government Offices & Public Schools Post Office - Marion 209 N Broadway Ave Marion, SD 57043 Phone : (605) 648-3210 Business Category Government Offices-City Village & Twp Post Offices Government Offices State & Local Government Offices & Public Schools Toll-Free           (800) ASK-USPS Fax           (605) 357-4906