Sullivan is a city in Moultrie County, Illinois, United States. The population was 4,413 at the time of the 2020 census. It is the county seat and largest city of Moultrie County. Sullivan is named after Sullivan's Island, South Carolina, where Fort Moultrie is located. History Sullivan was founded in 1845 as Asa's Point. Two years after Sullivan was founded, the first official courthouse of the county was built. It was a simple two-story brick building with a hipped roof, and the county jail was housed in the basement. The village would come alive with gossip when court was in session. Abraham Lincoln passed through this first courthouse many times from 1849 to 1852 as he practiced law in the Moultrie County circuit court. The present courthouse (the county's third) contains a mural depicting this first courthouse. In the opinion of early local leaders, Sullivan was not a logical site for a county seat. The village of Nelson (which no longer exists) had already been developed, and the prairie on which Sullivan would be built lacked proper drainage and was a breeding ground for malaria-carrying mosquitoes. In 1844, however, it was determined that centrally-located Sullivan was to be the county seat. The original village consisted of 40 acres (25 city blocks) bounded by Jackson Street on the north, Water Street on the south, Douglas (now Worth) Street on the East, and Hamilton Street on the west. Sullivan's first school was built in 1846, with the first church being built in 1848. When Abraham Lincoln was campaigning for the state senate against Stephen A. Douglas, he gave a speech in Freeland Grove (now the Sullivan Civic Center parking lot). Freeland Grove was bounded by Wyman Park, Main Street, Strain Street, and Worth Street..There is now a small monument commemorating Lincoln's 1858 speech that faces Wyman Park near Main Street. During this campaign, a riot broke out on the town square between the supporters of Lincoln and the supporters of Douglas. In 1864, a fire destroyed the first courthouse and a second, larger one was built that was in use until 1904, when it was demolished and the third, present-day courthouse was built. Along with the first courthouse building, hundreds of county records were lost. Sullivan was also home to the Titus Opera House, built in 1871, which was located on the north side of the town square. On the second and