39A: Squarest of the 50 states (WYOMING) is the theme here. Does that mean simply in terms of geometry, or is there a snipe in there? Regardless, it's pretty clever to find four well known attractions or sights in the state, each of which is 11 letters long. And the four are placed to create a square in the middle of which is the state's name. Very nice.
It's odd also to see OLDFAITHFUL so soon after the Sunday, August 21 puzzle featured it geysering up through Yellowstone. I personally have never set foot in Wyoming, for no particular reason, so I have never visited any of these sites. DEVILSTOWER of course was the site of Close Encounters of the Third Kind's ET landing. Do you remember Richard Dreyfuss turning his mashed potatoes into a model of the butte?
In other news, the fill is reasonably good. Any mention of a SAMOSA and IMOKAY with that. I smiled at MANSMAN. Count me out for ECOLI though.
1A: Apple computers (IMACS) gets a C for average. I also put it in as my first confident answer.
And that's about that... Except, I learn that Mr. Steinberg actually placed the theme answers in geographically appropriate parts of the grid as well! That is a nice touch.