Coopers Corner 51 State Route 23 Colfax, WA 99111 Phone : (509) 397-3395 Business Category Nonclassifiable Establishments Post Office - Steptoe 100 Steptoe St Steptoe, WA 99174 Phone : (509) 397-3395 Business Category Post Offices Toll-Free           (800) ASK-USPS