I'm pretty sure this is a nighthawk. I saw two of them on this fence rail in Scenic yesterday. They had their backs to me and I took photos from the road, from the car window. I could tell they were a new sighting for me and I didn't want to scare them off. As the bird guide points out, they were perched parallel to the rail, not facing outward as most birds do.
The town of Scenic, SD is along Hwy. 44, which runs S. of I-90. The Longhorn Saloon is just a popular photo op now. The town's population in 2000 was 87.
This is part of the panoramic view from the top of Sheep Mt. in the Southern section of the Badlands, just 60 miles E of the Eastern Black Hills area. Most visitors don't see this area. The popular loop drive is in the Northern area off of I-90.