Camp Siegfried:
It was "a summer camp which taught Nazi ideology, was located in Yaphank, New York, on Long Island. It was owned by the German American Bund, an American Nazi organization devoted to promoting a favorable view of Nazi Germany, ...". It "was one of many such camps in the US in the 1930s, including" ones in Grafton, WI, in Andover, NJ, in Sellersville, PA, and in Windham, NY.

#History
https://en.wikipedia.org/wiki/Camp_Siegfried
http://konreioldnewyork.blogspot.com/2014/10/camp-siegfried.html

@nealfig Maxwell Smart's recurring antagonist was named Siegfried. I wonder if the writers chose that as a reference or it's just a coincidence.