The section of present-day Wyo 270 from U.S. Route 26, east of Guernsey, north to Hartville at present-day WYO 318 was formerly designated as Wyoming Highway 318 prior to the 1970s. WYO 318 used to begin as US 26 at Guernsey and end at Sunrise with a 90degree turn at Hartville. The stretch between Guernsey and Hartville was recommissioned as Wyoming Highway 270 when that road was completed between Manville and Hartville to maintain continuity.