10 U.S. Landmarks That Have Left Experts Stumped – And 10 Whose Mysteries Have Now Been Unraveled

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The United States has many stunning historic sites – no small number of which date from millennia before European settlement of the land. Careful study of some of these archeological gems has revealed their secrets, but other sites have baffled researchers with enduring and intriguing mysteries. Read on to find out about some of these outstanding sites – from the explained to the enigmatic.