About Us

New Castle, a one-mile square island in the mouth of the Piscataqua River, has a fascinating history. Settled as a fishing village, it became the capital of the province of New Hampshire in the late 1600s. The first overt act of the Revolutionary War took place in New Castle at Fort William and Mary. Over the following years, military fortifications were constructed on the island to defend the strategic and vital entrance to Portsmouth Harbor. Many of the original island families continue to preserve New Castle’s history through their generous donation of historic documents, maps, books, photographs and artifacts. As a quaint and picturesque village, New Castle weathers the changes of time with grace and fortitude. Come to the museum and experience New Castle’s unique history.

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The History of the Old Library Museum

The New Castle Historical Society is housed in The Old Library Museum building which stands on Windmill Hill in New Castle. It was originally built as a church in the mid-1800s by disciples of Benjamin Randall, a New Castle native and founder of the Free Will Baptist Church.

In 1923, the few remaining members of the church gave their building to the town. The belfry was removed and the building remodeled for use as a library.  It served the town as a library until 1980 when the library moved to the new recreation building at the Great Island Common.

The building remained vacant until 2002, when the New Castle 
​Historical Society moved to protect the building from being  demolished, with plans to convert it to a museum to house the New Castle Historical Society. After a substantial renovation, the Historical Society opened in 2006.

Sailboats off the Portsmouth Yacht Club

New Castle Schoolteacher Maude Hayes Trefethen (1874-1956), circa 1892.