Ottawa is a city located at the confluence of the navigable Illinois River and Fox River in LaSalle County, Illinois, United States. The Illinois River is a conduit for river barges and connects Lake Michigan at Chicago, to the Mississippi River, and North America's 25,000 mile river system. The population estimate was 18,742, as of 2020. It is the county seat of LaSalle County and it is the principal city of the Ottawa, IL Micropolitan Statistical Area. History Ottawa occupies a place on the Illinois River that has long been one end of a portage trail between the Mississippi River and Lake Michigan. Here the river was reliably deep enough for canoes. The North Portage Trail connected the site over land and water to the Chicago River. Ottawa was the site of the first of the Lincoln–Douglas debates on August 21, 1858. During the Ottawa debate, Stephen A. Douglas, leader of the Democratic Party, openly accused Abraham Lincoln of forming a secret bipartisan group of Congressmen to bring about the abolition of slavery. The John Hossack House was a "station" on the Underground Railroad, and Ottawa was a major stop because of its rail, road, and river transportation. Citizens in the city were active within the abolitionist movement. Ottawa was the site of a famous 1859 extrication of a runaway slave named Jim Gray from a courthouse by prominent civic leaders of the time. Three of the civic leaders, John Hossack, Dr. Joseph Stout and James Stout, later stood trial in Chicago for violating the Fugitive Slave Act of 1850. Ottawa was also important in the development of the Illinois and Michigan Canal, which terminates in LaSalle, Illinois, 12 miles to the west. In 1838, workmen from the canal project were causing public unrest. During a citizens' meeting, a local political leader, Washington Armstrong, suggested that farmer William Reddick be elected sheriff. Reddick was a popular choice due to his large stature and courageous manner. Reddick was elected by a large majority and held the office of sheriff for four consecutive two-year terms. In 1855, while serving in the Illinois State Senate, Reddick commissioned the construction of a large Italianate house for the then-large sum of $25,000. Reddick Mansion is now one of the largest surviving homes in Illinois to predate the Civil War. In 1973, the mansion was added to the National Register of Historic Places, as part of