Illinois was part of the French colonial empire, and the city of Cahokia, located near present-day Collinsville, was one of the largest pre-Columbian cities in North America. At its peak, around 1250 CE, Cahokia had a population of around 20,000 people.
Adams County, Illinois has a rich and storied history dating back to its origins in the early 19th century. The county was established on January 13, 1825, and named after the sixth President of the United States, John Quincy Adams. The area was initially inhabited by indigenous Native American tribes, including the Illini and Mesquaki tribes, before European settlers arrived.

In the early years of settlement, Adams County played a significant role in the development of Illinois as a state. The first permanent European settlers in the region were French traders, who established trading posts along the Mississippi and Illinois Rivers. As American settlers began to arrive, the county quickly grew in population and economic activity.

The city of Quincy, which is the county seat of Adams County, became a major hub for steamboat traffic on the Mississippi River during the mid-19th century. The river served as a vital transportation route, connecting the area to larger markets in St. Louis and New Orleans. This led to the rise of industries such as lumber, brick making, and manufacturing in the county.

During the Civil War, Adams County played a critical role in supporting the Union cause. Quincy became a strategic location for military recruitment and supply, and many residents joined the Union Army. The county also served as one of the many stops on the Underground Railroad, providing a safe haven for escaped slaves seeking freedom.

In more recent years, Adams County has continued to thrive as a center for agriculture, manufacturing, and healthcare. The county is known for its fertile farmland, producing a variety of crops including corn, soybeans, and wheat. Quincy has also become a regional hub for healthcare, with numerous hospitals and medical facilities serving the area.

Today, Adams County remains a vibrant and diverse community, with a rich history that is celebrated and preserved through its numerous historical sites and museums. The county's strategic location on the Mississippi River, its contributions to the Union cause during the Civil War, and its agricultural and industrial sectors continue to shape its present-day identity.

This timeline provides a condensed summary of the historical journey of Adams County, Illinois.

  • 1825: Adams County, IL is established
  • 1839: Quincy becomes the county seat
  • 1841: The Mormon Temple is built in Nauvoo
  • 1861-1865: Adams County residents serve in the American Civil War
  • 1871: Quincy suffers a destructive fire
  • 1898: The Adams County Courthouse is completed
  • 1920: The Lock and Dam No. 21 is constructed along the Mississippi River
  • 1940: The Great River Road is established in Adams County
  • 1954: Interstate 172 is completed, connecting Quincy to the Interstate Highway System
  • 1979: The Quincy Notre Dame High School is founded
  • 1993: The Great River Bridge is opened between Quincy and West Quincy