With the 1st pick of the 39th Round (1157th overall), the Astros select 6'4" 240lb RHP Juan Carlos Santos from Arlington Country Day School, FL.
Not much is found on Juan Carlos, but I saw one report that says his fastball runs around 91 mph. If you're able to get it to load (I couldn't on my laptop, but could on the ipad), here's video of one of his showcase games.