Mountain laurel was designated as Pennsylvania's official state flower in 1933. Mountain laurel is an evergreen shrub native to the eastern United States (from southern Maine to northern Florida and west to Indiana and Louisiana).

Mountain laurel is also called ivybush, calico bush, sheep laurel, lambkill, clamoun, and spoonwood (native Americans used to make spoons from the wood). The mountain laurel is one of the most beautiful of native American shrubs. The fragrant star-shaped white and pink flowers have attracted travelers since early colonial days (first recorded in America in 1624).

Source:

Pennsylvania - Symbols: PA Historical & Museum Comm.
State Symbols: Hello Pennsylvania

Links:

State Flowers - 50 States List
National Flower