Our Pick
Posted on @rawstates
Colt's armory
1855
Hartford, Connecticut
Public domain · Wikimedia Commons
Samuel Colt built a factory under a blue onion dome and pushed interchangeable parts far enough that it became known as the American system of manufacturing. Elizabeth Colt ran the company for decades after his death, and the plant later made Gatling guns and early Pratt & Whitney engines.
That was 1 of the hidden places.
Location: documented spot
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