Post Office - Harrisburg 307 E Willow St Harrisburg, SD 57032 Phone : (605) 743-2791 Business Category Post Offices Toll-Free           (800) ASK-USPS Fax           (605) 357-4906 United States Government--harrisburg, Post Office 323 Willow Harrisburg, SD 57032 Phone : (605) 743-2791 Business Category Government Offices-Federal Post Offices Government Offices & Public Schools