Complex sentence: Morgan Avenue opened on July 14,1928 as part of an eastern extension of the Canarsie Line from Montrose Avenue, which opened four years earlier, to Broadway Junction, connecting afterward to the already-operating elevated line to Canarsie.
Split into simpler sentences: Morgan Avenue opened on July 14,1928, as part of an extension of the Canarsie Line. This extension connected Montrose Avenue, which had opened four years earlier, to Broadway Junction, which was the western end of the already-operating elevated line to Canarsie.