I am considering an award routing on United to ROM (ORD-DCA, IAD-ROM) with various 3 to 6 hour layover options. My thought was that this might offer the opportunity to do some taxicab-type sightseeing in DC since we've never been there.

We will have large checked suitcases that I was asssuming would be checked for free at ORD since we have a transcontinental flight. Can anyone explain if indeed our luggage would be free of charge on an itinerary such as this, and if sightseeing within such timeframes is realistic?