Here is a link to a bio for Seth Benjamin Tanner on Wikipedia. There is some good information I had not seen before, and links to information on Tanner Trail in the Grand Canyon.
http://en.wikipedia.org/wiki/Seth_Tanner
This is another great link with information on the Grand Canyon, with details about Tanner Trail and Seth Tanner. “This site is part of a multi-media educational project,“Nature, Culture, and History at the Grand Canyon”.
http://grandcanyonhistory.clas.asu.edu/sites_rimtoriverandinnercanyon_tannertrail.html
Seth Benjamin Tanner: Photo from Grand Canyon Museum Collection, Catalog # GRCA 7060A, posted on the NCHGC site above
The marker at Cameron Bridge, near the spot formerly known as Tanner’s Crossing: First posted on TheAncestorFiles.blogspot.com
On Granny's Trail 
Oh, Seth! I’ll bet you could have smiled for the camera if you had really tried….Maybe he was just really tired from crossing the canyon without the bridge.
:-))