So today I went to the Special Collections at the University of Oregon in Eugene. http://libweb.uoregon.edu/speccoll/ They have some original Frederic Rodrigo Gruger drawings and a bunch of originals from other artist of his time. I can't post the pictures that I took there, but I can post some pictures from his book that I would highly recommend. UVU has this book in its library.
Seeing the originals of great artists is so inspiring. The brush strokes, smudges, old white gouache that has turned blue, pen and ink!! I have been a big fan of Gruger for a long time. I pick up his book at least once a week. These are a few pictures from his book.