1. Grand Canyon National Park, Arizona
> Visits in 2018: 6,380,495
> Change in visits from 2017: 2.0%
Most people don’t picture trees when they think of the Grand Canyon, and that may be because most visitors only stop at the South Rim. The North Rim of the canyon, while less accessible, is lined with aspens, birches, and oaks and is the best spot in the park to see fall colors. Late September to mid-October are ideal times to visit, as the North Rim closes at the end of October.