This route is best run in the direction mapped (South Kaibab > Tonto > Bright Angel), not reversed. Water is unavailable on the South Kaibab or Tonto Trails, while Bright Angel offers both seasonal and year-round sources. Runners should utilize a hydration vest or similar and consider an early start during the intense summer heat. Though the least challenging portion of the run, Tonto Trail is lined with low-growing brush and almost no shade.

Worth noting, every morning at 5am a mule train departs down South Kaibab Trail to deliver supplies to Phantom Ranch. While you only spend ~4.5 miles on South Kaibab, be mindful as you may still encounter them on your trek down.

Though a classic and favorite among hikers, runners, and backpackers today, this loop wasn't possible in the park's earlier years. When the Grand Canyon was first added into the National Park System in the early 1900s, the only way into the canyon was by way of the Bright Angel Trail. At the time, a local named Ralph Cameron charged visitors a toll to utilize the trail and "refused to give up his claim" when asked. According to this article, "National Park Service officials decided to build their own trail. They achieved this by constructing the South Kaibab Trail and later the North Kaibab Trail to complete the first trans-canyon trail in the popular Grand Canyon Village area. Experienced engineers and miners perfected techniques for creating inner-canyon trails by their work on the South Kaibab Trail."

Sources: http://earlyrisehiker.com/2016/04/south-kaibab-tonto-bright-angel-loop/ http://grcahistory.org/sites/rim-to-river-and-inner-canyon-trails/south-kaibab-trail/