Complex sentence: Springfield is the capital of the U.S. state of Illinois and the county seat of Sangamon County with a population of 116,250, as of the 2010 U.S. Census, making it the sixth most populated city in the state.
Split into simpler sentences: Springfield is the capital of the U.S. state of Illinois and the county seat of Sangamon County. The city has a population of 116,250, as of the 2010 U.S. Census, making it the sixth most populated city in the state.