Waukegan, first visited by Pere Marquette in 1673, is one of the oldest communities in Illinois. The city started as a French trading post and Potawatomi Indian settlement known as "Little Fort". Records dating back to 1829 tell of a treaty signed by the Potawatomis in which they ceded all of their land in this area to the Federal Government.Little Fort became the County Seat of Government in 1841 by virture of its population. Between 1844 and 1846, the town's population grew from 150 to 750 people. In 1849 when the town was incorporated, the population had risen to 2,500.Proud of the growth of their community and no longer wanting to be characterized as "little", on March 31, 1849 the residents of Little Fort changed the name of their town to Waukegan, the Potawatomi word for "fort" or "trading post".

Early settlers were initially attracted to Waukegan as a port city and shipped produce and grain from Lake and McHenry County farms to Chicago. The creation of the Illinois Parallel Railroad (now the Chicago & Northwestern) in 1855 stimulated interest in Waukegan as a manufacturing center. The town continued to grow and diversify, and Waukegan was incorporated as a city on February 23, 1859, with an area of 5.62 square miles.