The Williamson House was built in 1844 for prominent lawyer, editor and businessman Joseph Williamson by the renowned Maine architect Calvin Ryder. In 1877 Williamson published a History of Belfast covering from the earliest of time to 1875 in a 956-page volume, and left a second volume ready for publication bringing the History of Belfast to the end of the 19th century.

When the house was completed in 1845, it was magnificent for the day. The exterior has a neoclassical style that was very popular during the Greek revival period. This design was carried throughout the inside of the house as well where the finest of materials were used in this superbly constructed year-round residence. It is believed that like many architects, Ryder was influenced by the English architect, Sir Christopher Wren (1631-1723), whose pinnacle project was St. Paul's Cathedral in London

The property has been owned by prominent families from Philadelphia, Boston, New York and Chicago and used both as a summer cottage as well as a year-round residence.

In 1920 a major effort to expand and modernize the residence was undertaken, expanding the North and South wings, adding modern plumbing conveniences and re-designing the porte-cochere with an eye toward maintaining architectural integrity. The property was restored most recently in 2005/06

Today the property has been restored to include safe and secure conveniences while ensuring the historic nature of the National Registered Historic District are maintained.