Complex sentence: Orange is unusual in that many of the homes in its Old Town District were built prior to 1920; whereas many other cities in the region demolished such houses in the 1960s, Orange decided to preserve them.
Split into simpler sentences: Orange is unusual in that many of the homes in its Old Town District were built prior to 1920. While many other cities in the region demolished such houses in the 1960s, Orange decided to preserve them.