Dan Tilque's The Purple Turtle in the August 2004 issue demonstrated that some of the simplest ideas are often the most appealing. There are 325 possible substitutions (not 375), and Dan listed 224 of these (not 277). Extending the search to include the Oxford English Dictionary, Second Edition (oed), etc., and locations other than US place names, I managed to fill at the gaps.
"More Purple Turtles (Part 1),"
Word Ways: Vol. 37
, Article 8.
Available at: http://digitalcommons.butler.edu/wordways/vol37/iss4/8