Are there any endurance races in the Dallas/Fort Worth area?

I've been riding for about a year and have been focusing on endurance. My typical ride is around 60 miles with the occasional 80 or 100 mile ride. So, when I say race, what I really mean is a single day event where there is a starting and end point. Something like Tour De Donuts comes to mind. Something that some people might take seriously, but others just want to participate in an event.