Check out a fantastic Minnesota State Park just across the border from Sioux Falls called Blue Mounds State Park. We met a number of people there that were from Sioux Falls. They said it was the closest decent SP near Sioux Falls. Here's a link:
http://www.dnr.state.mn.us/state_parks/blue_mounds/index.html
Great bike and hiking trails. Shaded camgground with new individual bathroom/showers accessed from the outside. Swimming area was OK. It's on a river and wasn't crystal clear. And the park has it's own Buffalo Herd roaming in a pasture on the property. Very cool!
Andy
1 DW, 2 DD(Twins,5), 2 DS (7 & 8)
2008 Roo 233
2004 Toyota Sequoia
Pro Series WD, Reese sway control