
According to Maine's Lakes Environmental Organization, one Crystal Lake "is the only lake completely within the borders of Harrison. Mill Stream, which is the outlet of the lake, provided early village settlers with power to run both a grist and saw mill." [Source] The second Crystal Lake is has its own Crystal Lake Association, formed in 1970, whose website has some beautiful photos.
Back in 1963, the New Yorker, of all sources, reported on how Anonymous Pond (now Crystal Lake in Harrison) was about to lose its anonymity: "Incidental Intelligence: In Cumberland County, Maine, there is a body of water that has the arresting name of Anonymous Pond. Now some spoilsports are trying to have it officially called Crystal Lake, and it may become anonymous." [Source: John McCarten, Incidental Intelligence, The New Yorker, March 2, 1963, p. 24, read abstract here]
Anonymous Pond, though quiet in recent years, has a lively history, including one of Maine's first alligator captures. Yes, I said alligator! To quote Chris Dunham, over at All Things Maine, "The first [recorded alligator in Maine] was probably the one shot in Owlsley Cove, Anonymous Pond (Crystal Lake) in Harrison in November of 1895." You can read a full account here, but I will tantalize you with this tidbit: "The alligator was first seen by W. M. Shaw of South Paris. In company with other members of the Owlsley club he was returning from Harrison with a load of provisions when he noticed a large black object floating on the sunlit waters of the quiet little cove, near which the camp of the Owlsley club is situated. ... During Friday and Saturday the mysterious creature was occasionally seen by various persons, and shot at several times without apparent effect."