The Thunder River Trail was originally constructed in 1876 when rumors of a gold find along the Colorado River required some type of access route to the Deer Creek area. The current trail which goes down to Thunder River and Tapeats creek was not constructed until 1926.
Thunder River is the world's shortest and probably steepest river.
The trailhead for the Thunder River Trail is located at Indian Hollow. To get to Indian Hollow you can basically use the same directions for getting to the Bill Hall Trail at Monument Point. Just remember to keep following the signs for Thunder River signs and take the right turn around mile 29.5. I have not done the top 5 miles of this trail myself so I cannot attest to its difficulty. Most people will tell you to use the Thunder River Trail as opposed to the Bill Hall Trail if you are planning a hike in this area because it is much easier.