I've been reading a lot of biographies lately, and find they're a great way to learn a bit of history (my history classes in school were pretty bad). I recently finished "Undaunted Courage," which is a biography of Meriwether Lewis, and am currently reading Dorris Kerns Goodwin's book about Roosevelt, Taft and the muckrakers, and I was struck by the yawning gulf between knowing nothing about anything west of the Mississippi at the beginning of the 18th century, and to having everything settled at the beginning of the 19th.

I've obviously heard about "the wild west" in pop culture, but is there a good book or biography that you'd recommend that would give me a sense of that time period?