Canonsburg, borough (1990 pop. 9,200), Washington co., SW Pa., inc. 1802. Its steel and coal industries have declined significantly. A gram of radium produced there was presented to Marie Curie in 1921 when she visited the town. The Log Cabin School (est. 1777; the first school west of the Alleghenies) is preserved. The Black Horse Tavern was a famous gathering place for leaders of the Whisky Rebellion (1794). Roberts House (1804) is an example of W Pennsylvania manor architecture.