One of my favorite books when I was 12 years old, parallels the expedition of Coronado in 1539, as he travels through the Southwest and California.
a gppd adventure
Read this when I was 14 (several times), now that I live in the area that the protaganist travelled through, it's even more interesting, although I'm having trouble finding the places, I think Scott O'Dell took some liberties with geography. (no "inferno" in northwest Arizona, the mud craters are in California, not Arizona.) It's a story about a 15 year old cartographer who travels with Coronado, and takes a side adventure from the main body of Coronado's army. A little bit of a love story added.