A tour of Portsmouth's famous houses is like a tour through time, with Colonial and Federal architecture from 1684 into the 19th century. One-time capital of New Hampshire, Portsmouth was also the home port of a dynasty of merchant seamen who grew rich and built accordingly. The old atmosphere still exists in the narrow streets near Market Square.

The US Navy Yard, located in Kittery, Maine, on the Piscataqua River, has long been Portsmouth's major "industry." The peace treaty ending the Russo-Japanese War was signed at the Portsmouth Navy Yard in 1905.