Complex sentence: The then smaller village of Buffalo Grove and a section of Prospect Heights were included in the plan in order to create a larger tax base, with the combined population of the areas was only about 8,000 at that time.
Split into simpler sentences: The then smaller village of Buffalo Grove and a small portion of Prospect Heights were included in the plan in order to create a larger tax base. The combined population of the areas was only about 8,000 at that time.