Statistics for occurrence #1 of “Spy pond” in chapter 10 of Medford Historical Society Papers, Volume 15.:

...er and Lower Mystic lakes. Should one be built, it may be possible to go from Boston to Lake Innitou (choose between this name, Horn pond or Lake of the Woods of 1819) by motor boat, as well as to Spy pond in Arlington or Fresh pond in Cambridge, as Winchester is planning a water park all its own. Under date of May 2, 1856, Caleb Swan interleaved his copy of Brooks' history with the following:&mdas...
Max. Freq. Min. Freq.
Entity Corpus Doc Corpus Doc  
Spy Pond (Massachusetts, United States) 64 2 0 0 0 user votes
Spy Pond (New York, United States) 2 0 0 0 0 user votes

† This entity has been selected by the automated classifier as the most likely match in this context. It may or may not be the correct match.