The winter ranges of the Northside mule deer herd can be broadly separated into northern and southern subgroups. The majority of the southern subgroup winters at low elevations near the John Day River in areas dominated by big sagebrush communities, Columbia Basin grasslands, and western juniper. The northern subgroup is more spatially dispersed, wintering by Cottonwood Creek, the North Fork John Day River, and the Middle Fork John Day River in ranges containing more conifer forest than those of the southern subgroup. Both subgroups summer in the same general area, migrating either northeast or southeast to reach ranges featuring mixed-conifer, Picea spp. (spruce), Ponderosa pine, and western juniper forests with scattered Columbia Basin grasslands on Deardorff Mountain, the Blue Mountains, and Elkhorn Ridge. Some mule deer west of the North Fork John Day River migrate north to reach summer ranges near Rock Creek. Interestingly, five mule deer migrated south, crossing the section of U.S. Route 26 that divides the Northside and Murderer’s Creek mule deer herds. Since U.S. Route 26 also separates resident mule deer from agricultural fields with reliable water sources, mule deer-vehicle collisions are common year-round, and this section experienced an annual average of 106 mule deer-vehicle collisions from 2016 to 2022. In 2010, the Heppner WMU, which is used for livestock grazing and contains multiple mule deer winter ranges, was included in the Oregon Mule Deer Initiative (ODFW, 2015, 2020). Since then, ODFW has removed 10,256.7 acres (4,150.7 ha) of invasive flora, reseeded 7,405.3 acres (2,996.8 ha) with native shrubs and grassland, and completed 48 water development projects. These mapping layers show the location of the winter ranges for mule deer (Odocoileus hemionus) in the Northside population in Oregon. They were developed from 239 migration sequences collected from a sample size of 114 animals comprising GPS locations collected every 5−13 hours.