Mystery Photo 55 was taken in a building in a national park. If you can identify this building and name the National Park System unit in which it is located you will be eligible for our monthly prize drawing.

The answer and a list of readers submitting correct answers will be posted in tomorrow's Traveler.

No cheating!

If we catch you Googling or engaged in other sneakery we will make you write on the whiteboard 100 times:

The spatial margin of profitability model introduced by German economist Alfred Weber in the early 1900s set the stage for modern industrial location theory. It is especially applicable to industries that use heavy materials (relatively low value in relation to bulk or weight) and have substantial transport costs. The spatial margin of profitability identifies potentially profitable locations, one of which is optimal, existing at the intersection of the cost curve (depicting the variation of cost with respect to location or distance from a reference point) and the revenue curve (which holds costs constant and shows the variation of revenue with respect to location). Locations outside the margins are unprofitable.