Connellsville dates back to the early 19th century, but it did not become a city until 1909, when the borough of Connellsville and its neighbor across the Youghiogeny River, the borough of New Haven, were joined together. While Connellsville is famous for being the center of the coke industry in western Pennsylvania during the late 1800s, New Haven was at the center of a spectacular quadruple murder in 1893.