Cook County, Illinois: History
Cook County was created on January 15, 1831, out of Putnam County by an act of the Illinois General Assembly. It was the 54th county established in Illinois and was named after Daniel Pope Cook. As a politician, lawyer and newspaper publisher from the U.S. state of Illinois as well as an anti-slavery advocate, Cook became one of the earliest and youngest statesmen in Illinois history. He served as the second U.S. representative from Illinois and the state's first attorney general. In 1839, DuPage County was carved out of Cook County.
The shape of Cook County and the neighboring counties has remained the same since DuPage County was formed. The population in each county and the split of agriculture compared to residential and industrial activity has changed dramatically over the intervening decades to 2020. The county began with 10,201 people in the census of 1840, growing rapidly to 5,150,233 people estimated for 2019 by the US census. Growth was rapid in the 19th century, with the County reaching 2.4 million people by 1910. In the 20th century, the County reached 5.1 million population.
Cook County is nearly completely developed, with little agricultural land remaining near the outer county boundaries.