Many US National Parks charge an admission fee, and the Grand Canyon, which is high on many a bucket-list, is one of them. However, if you visit on a handful of national holidays and milestones (including the National Park Service’s birthday and Veterans Day) you’ll be able to enter the Grand Canyon, and all other sites in the National Park Service system, for free. Be aware, though, that waived entry fees means sites are likely to be busier than normal, and charges may still apply for campgrounds, guided tours etc.