Complex sentence: In December 1982, the Louisville & Nashville Railroad merged with the Seaboard Coast Line Railroad to form the Seaboard System, and finally, in 1986, the Chessie System and the Seaboard System merged to become CSX Transportation.
Split into simpler sentences: In December 1982, the Louisville & Nashville Railroad merged with the Seaboard Coast Line Railroad to form the Seaboard System. In 1986, the Chessie System and the Seaboard System merged to become CSX Transportation.