The Phelps Mansion, formerly known as The Monday Afternoon Clubhouse, is a three-story brick and stone mansion located on Court Street in Binghamton, New York. It was built in 1870 as the private home of Sherman D. Phelps. Mr. Phelps was a successful businessman, banker, Republican elector for Abraham Lincoln, and mayor of the City of Binghamton. The building was designed by Isaac G. Perry who later became the chief architect for the New York State Capitol building in Albany, New York. The Phelps Mansion was charted by the New York State Board of Regents as a museum in 2005.