Hunt for the nation's oldest monuments, and prepare to get muddy

Placed in the 1790s, D.C.'s boundary stones delineated the borders of the capital city, with 36 of the original 40 still remaining but largely unnoticed by tourists.

Stephen Powers, an expert on D.C.'s boundary stones, organizes tours to visit all 40 stones, which are now largely hidden outside the busy downtown areas, reflecting the history of Washington's early growth.

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