Post Office - Parker 125 S Main Ave Parker, SD 57053 Phone : (605) 297-4440 Business Category Post Offices Toll-Free           (800) ASK-USPS Fax           (605) 357-4906 United States Government--postal Service Parker 125 S Main Ave Parker, SD 57053 Phone : (605) 297-4440 United States Government--postal Service Parker Business Category Government Offices-Federal Government Offices & Public Schools