The following are important events in the history of Lee County.

1778 Illinois became a county of Virginia after Americans captured Kaskaskia, the British seat of government. Virginia relinquished its claim in 1784.

1787 Congress made Illinois part of the Northwest Territory. The Northwest Territory was divided in 1800, when Illinois became a part of Indiana Territory.

1809 The Illinois Territory was formed when the Indiana Territory was divided.

1818 Illinois became a state, after the Wisconsin region was transferred to the Michigan Territory.

1828 Joseph Ogee Starts first ferry at what is now Dixon.

1829 Post Office established at Ogee's Ferry.

1830 John Dixon leases ferry from Ogee.

1832-33 Black Hawk War

1836 Last Indians leave area

1836 Ogle County organized, December

1838-56 Improvements in transportation hastened immigration to the northern counties. The National Road reached Vandalia in 1838. The Illinois-Michigan Canal opened in 1848. The Illinois Central Railroad was completed in 1856.

1839 Lee County established, 27 Feb 1839

1850 Civil townships organized

1854 First railroad

1861-65 Over 2,400 Lee County men served in the Union armed forces during the Civil War.

1871 Fire destroyed much of Chicago.

1873 Truesdell Bridge collapse

1876 Amboy Depot Built

1900 The current Lee County Courthouse was built

1919 Dixon War Memorial Arch

1933 Lincoln Bridge and Lincoln Statue

1942 Green River Ordnance Plant

1966 Sauk Valley College

1985 The Lee County Courts Building was built