Sangamon County, Illinois was formed in 1821 from Bond and Madison Counties, Illinois. The County was named for the Sangamon River, which runs through it. The name of the river comes from a Pottawatomie word Sain-guee-mon (pronounced "sang gä mun") meaning "where there is plenty to eat."
Prior to being elected President of the United States, Abraham Lincoln represented Sangamon County in the Illinois Legislature. Lincoln, along with several other legislators, was instrumental in securing the Sangamon County seat, Springfield, as the state's capital. Sangamon County was also among the area represented by Lincoln when he served in the US House of Representatives. Another legislator who represented Sangamon County was Colonel Edmund Dick Taylor, also known as "Father of the Greenback." The prominent financiers and industrialists Jacob Bunn and John Whitfield Bunn were based in Springfield, Sangamon County, Illinois, as well as in Chicago, during the nineteenth century and the early twentieth century. The careers of these men and the people with whom they collaborated helped to shape much of the history and development of Sangamon County, Illinois.
According to the 2010 census, it has a population of 197,465, which is an increase of 4.5% from 188,951 in 2000. According to the 2010 census, the county has a total area of 877.02 square miles, of which 868.30 square miles or 99.01% is land and 8.72 square miles or 0.99% is water.