This was a very SHORT-term visitor to our Backyard.
I was working in my computer room, second floor, which has a view of the back yard. I heard a righteous uproar...the sound of several Blue Jays screeching for all they were worth. Looking out, I saw this big black bird sitting on the peak of my shop roof...with three different Blue Jays dive-bombing it. It was unimpressed.
I'm going to guess this is a crow. It dwarfed the jays...but they were determined to drive it off. The crow stayed in place long enough for me to grab the camera, scurry downstairs and shoot a few pix through the back door. It then lifted off and flew to the top of a towering tree in a neighbor's yard...
...where the Blue Jays continued to harass it until it finally left the area.
UPDATE: After a lot of photo comparisons, this has been judged to be an American Crow. It is very similar to a Northwestern Crow in appearance...but those crows are NW US Coastal birds, living on shellfish etc. Since the don't migrate, finding one in Iowa would be like finding a swordfish in the Mississippi.