In an amusement park history book that came out in the 70's, it appeared that Marriott was planning to build 3 parks all at the same time - from the statements in the book, it sounded as if Marriott was actually about to break ground in DC.
Evidently there were some last-minute battles over real estate ownership that prompted them to pull out completely.
I believe they ended up just building 2 of the 3 proposed parks.
