I had a couple of ideas about what type of Hawk it was and Commenters put their two cents worth in. Turns out we were all wrong :)
I sent an email to the Blackland Prarie Raptor Center, which is a place where we send injured hawks and owls for rehab when I pick them up on the Job. They ID'd it as a Harlan's Hawk - which they explain is sort of a sub-species of Red Tailed Hawk.
It's not a common Hawk to see - so we can all use that excuse for getting it wrong :)