i tried searching it on google but it actually didn't help me at all
Question about The Grand Canyon
I think you can ride them all the way to the bottom and along the floor.
Not donkeys--mules. You can ride from the South Rim down to Phantom Ranch at the bottom or to Plateau Point 2/3 of the way down. backpackthegrandcanyon.com
From the North Rim (Mid May thru Mid Oct) you can ride down to the Supai Tunnel only. From South Rim you can go all of the way to Phantom Ranch at the very bottom of the canyon.