A series of small rapids, known collectively as the Roaring Twenties, give river runners a fast and fun run: North Canyon, Indian Dick (don’t ask), 23-Mile, 23.5-Mile, 24-Mile, 24.5-Mile Rapids, and so on, are a mild roller-coaster ride and a mere preview of things to come.

Harmless as it seems today, this section of canyon plagued Robert Brewster Stanton’s ill-prepared first attempt at running the canyon in 1889, and 25-Mile Rapids is also known as Hansbrough-Richards Rapids for the second and third men drowned on that fateful expedition.

The Supai Group of rocks, which begin to appear about 11 miles downstream from Lees Ferry, form the bedrock of beautiful North Canyon, entering from the west at mile 20. Shortly after that, cliff-forming Redwall limestone appears. This limestone, left by a shallow sea 320–360 million years ago, is actually off-white but stained reddish by the overlying layers. Throughout the canyon, Redwall cliffs are streaked with tapestries of desert varnish—dark manganese oxide stains.

Tributaries like Rider Canyon, South Canyon, and Buck Farm Canyon not only make fascinating day-hike opportunities for river runners but also offer backpacking adventures for people entering from the House Rock Valley area. Some tributaries have obstacles barring further progress from river or rim, so canyoneers often carry technical climbing gear to rappel down pour-overs (dry waterfalls) or small inflatable rafts to float packs across long, deep pools.