Springfield is the third and current capital of the U.S. state of Illinois and the county seat of Sangamon County with a population of 116,250, making it the sixth most populated city in the state. Present-day Springfield was founded in the late 1810s, around the time Illinois became a state. The most famous past resident is Abraham Lincoln, who lived in Springfield from 1837 until 1861, when he left for Washington, DC to become the 16th President of the United States.