Three Creek Century (Carlisle, PA)
If you aren't sure where Carlisle is...it is near the intersection of I-76 and I-81, about 20 miles west of Harrisburg. From Philly or DC it is about 2 hours, and 3 from Pittsburg, according to Google.
The goods. The Harrisburg Bicycle Club hosts a very well supported century based out of Carlisle every September. This year the ride is on Sunday, September 15. I am late posting this, as the early registration closed on the 15th, but there are still entries available in advance, $25 until August 30th and $30 after August 31st. Riders under age 18 are $5. Walk ups are usually available as well. For all of the details on the ride, check out their site: www.threecreekcentury.com.
The course provides three loops, all originating in Letort Park, in downtown Carlisle. Two 25 milers, and a 50 miler. None is terribly hilly, though one of the 25s is flatter than the other, and the 50 has some good roll in it. For cue sheets and GPX or TCX files, click the "Routes" tab on the ride's site.
I am signed up with some other folks I know here in DC and a couple of guys we know in Carlisle. Anyone else signed up or planning to sign up?