Unlike most of the rest of the world, lounge access within the United States comes primarily through membership. Even with top elite status on three airlines, I get no lounge access when traveling domestically on them. A typical exception is when traveling internationally, when Star Alliance Gold members can indeed access Star Alliance lounges.
This often leads people to believe - incorrectly - that when traveling domestically it's simply not possible to access a lounge.
But that's not quite what the rules say. The way the rules are written for Star Alliance actually makes specific exceptions for United Clubs and US Airways clubs, but not other Star Alliance Gold lounges:
This means that non-United and US Airways Star Alliance Gold lounges are actually accessible even on domestic trips!
Now, in practice this isn't quite as amazing as it sounds, since often foreign Star Alliance Gold lounges are simply not accessible from domestic terminals. This is true at almost all airports with foreign lounges, with one notable exception: Washington Dulles.
Washington Dulles has Lufthansa Senator & Business lounges near gate B49 that are perfectly accessible from the rest of the terminal. While little-known, it's entirely possible for any Star Alliance Gold member to walk right into the Senator Lounge with nothing other than their boarding pass and Gold card.
Even more strange is that with Lufthansa's separation of their Senator Lounge (for first class and Star Alliance Gold) and their Business Lounge (for business class), Star gold passengers on a $50 ticket flying 200 miles have access to a better lounge than full fare business class passengers flying across the Atlantic ocean!
Access to the IAD Lufthansa lounge must be little-known, otherwise why does one see hoards of United elites at the much-inferior United Club? One legitimate explanation is that, although accessible from other gates, the Lufthansa Senator lounge isn't particulary convenient if you're departing out of gates C & D - predominantly for United domestic departures.
Still, even when departing out of a far-off gate, I find it more than worthwhile making the trip to B49 to visit the Senator lounge.
I even go so far as to deliberately try to route myself through IAD simply to get a free (excellent) meal and shower while passing through.