The Josiah Mayo House located at 540 Main Street is an excellent example of life on Main Street in the 1800s. It was built between 1818 and 1820 by Josiah Mayo, a Blacksmith by trade, who was Postmaster in Chatham for 40 years, Treasurer for 27 years and Selectman for two years. The house was occupied by members of the family until 1938. In 1974 it was purchased by Cape Cod Five Cents Savings Bank, and two years later it became the property of the Chatham Conservation Foundation. The CCF has restored the house. Many local residents and visitors tour the Mayo House each summer.

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The Mayo House is open every Friday and Saturday from 10am-3pm.