Sioux Falls has a historic downtown area (with a few restaurants) close to the park with the falls. There's a local history museum which is pretty good, IIRC in the old courthouse building. Most of the other tourist stuff is in a different area of town.

IIRC the airport is on the same side of town as the Empire Mall and most hotels.

There's a Sheraton next to the Convention Center, on the opposite side of town.