What is today known as Overbook was originally called Fairhaven and was a small town within Baldwin Township. In 1871 the company of the Pittsburgh & Castle Shannon Railroad was incorporated with Milton Hays as its first president. The railway was important in the early expansion of the Fairhaven Community as it also served as a real estate development business. Plans of lots were on display at the company office. Overbrook was so named by Henry T. Galley, after Over-the-Brook, a town in Ireland. In 1919 the tiny but bustling town broke away from Baldwin Township and became the independent Borough of Overbrook. The development of local roads in the 1920s and the opening of the Liberty Tunnels in 1924 brought additional expansion for all southern communities.