I'd say much depends on your definitions of "hilly" and "flat." A few weeks ago a local racing club held their annual century. Most people who cycle in southern Maryland would consider their route hilly, but one of my friends met a couple of women from Pittsburgh who had come down for the ride, and they thought it was flat.

Some folks I know did the Covered Bridges ride last month, and the day before that they did their own ride using a cue sheet from the Lancaster club. There were two versions of the route. According to Ride with GPS, the 35-mile version had a total elevation gain of 1444 feet and the 42-mile version had a total gain of 2194 feet. Both rides started at the Strasburg Railroad Museum and went past the farm that was featured in the movie "Witness."