Taking its name from the DuPage River, DuPage was established as a separate county from part of Cook County in 1839, with Naperville as the county seat. In 1850, DuPage County was organized into nine townships, through the efforts of state legislator Warren Wheaton (1849–1851).

Throughout its history, DuPage County's growth and development have been linked to Chicago and to transportation routes in northern Illinois. When American settlers began arriving in the 1830s, the area that would become DuPage County was already crisscrossed by Indian trails. By 1800 the Potawatomi Indians had established four major villages along local rivers. In the 1830s stage routes radiating out of Chicago were established, with way stations in the area of the DuPage River. The first Euro-American settlers in the area were Bailey and Clarissa Hobson and their five children, who came from Orange County, Indiana, by 1832. Hobson built a gristmill on the West Branch of the DuPage River, near present-day Hobson Road, in Naperville. After the 1833 Treaty of Chicago forced the Indians to move west of the Mississippi River, white settlement accelerated. During the 1830s and 1840s, newcomers first claimed land along the branches of the DuPage River and then filled in across the prairies.