Walnut Canyon and Marshall Lake Professional Review and Guide
"According to ceramic dating and tree circles, there are signs that Sinagua Indian tribes have inhabited the Flagstaff area for 800 years. Just south of Flagstaff, though, there are signs of human habitation of caves along the walls of Walnut Canyon that are at least 2,000 years old. The “houses” built into the sides of the canyon help fill in many anthropological details, providing a look at the transitional centuries between year 0 and the years of flourishing Sinagua civilization. Walnut Creek has carved a canyon out of Kaibab Limestone as it flows seasonally toward the Little Colorado River, eastward, and eventually to the Grand Canyon.
Trail Surface: Both trails begin on the same old logging road, heading south away from Flagstaff into the canyons. Both trails later become singletrack. Some of the track atop Walnut Canyon is doubletrack and forest road; it’s all well marked with Arizona Trail signs, as both trails are part of this statewide network."