Photo @pedromcbride // Former Grand Canyon backcountry ranger Amy Martin watches a winter sunrise over a section of the Colorado called Conquistador Aisle. No trails exist along 95 percent of the canyon’s North Rim or along 80 percent of its South Rim. Fewer people have now hiked the canyon’s length in a single trip (10) than have walked on the moon (12). What will the next 100 years of our national parks look like? Full @natgeo story on newsstands now. #NPS100