Complex sentence: The movie was filmed in Eckley, Pennsylvania in 1968; which was so unchanged from its 1870s appearance that the only major alteration needed for filming was to remove television antennas and install underground electric.
Split into simpler sentences: The movie was filmed in Eckley, Pennsylvania in 1968. The town was so unchanged from its 1870s appearance that the only major alteration needed for filming was to remove television antennas and install underground electric.