This is a plug for an event which I help organize every year in Sioux City, Iowa. I kind of oversee keeping things organized and Jim Johnson is the Rally Master (or "Road King" as we call it) in charge of locations. The event is called the Big Sioux Rider Adventure Run. The format is basically a treasure hunt. All proceeds for the event go to a local charity called Opportunities Unlimited which works with folks who have brain and spinal injuries.
Many of the locations will be in the Loess Hills area which is a nice riding area with a lot of nicely paved, empty Iowa country roads with hills and gentle sweepers. We will try to point you towards all the best roads.
The past couple years we have been scheduling the event to coincide with another event in Sioux City called "Saturday in the Park" (SITP). That is July 5th this year. We don't have any official affiliation with that event, but the timing works out nice for us. SITP is a free public music festival. This year the headliner act will be Phil Lesh (Grateful Dead) & Friends playing at 8:45 PM. There will be other good acts that evening if you want to take in a band after the ride.
A local bar/entertainment center called the Ickey Nickel helps out providing free camping both Friday and Saturday night, and it is the end point of the ride. There are outside showers and facilities available. If you want information on camping call and ask for Jan (owner) at (712) 239-2772, or send your questions to me (Frump) "bjh att deadpacket dott com" or 253-4650.
Links:
http://www.bsradvride.org/
http://www.saturdayinthepark.com/