Within a century, the county recorded explosive population growth, going from a trading post village with a little over six hundred residents to four million, rivaling Paris by the Great Depression.

There are more than 800 local governmental units and nearly 130 municipalities located wholly or partially within Cook County, the largest of which is Chicago.

[6] The county is at the center of the Chicago metropolitan area, which has a population of approximately 10 million people.

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.

As of the fourth quarter of 2021, the median home value in Cook County was $299,571, an increase of 11.7% from the prior year.

Asian Americans made up 6.2% of the population (1.8% Indian, 1.2% Filipino, 1.2% Chinese, 0.7% Korean, 0.3% Vietnamese, 0.2% Japanese, 0.8% Other).

Sizeable non-Hispanic white populations are those of German (11.4%), Irish (10.3%), Polish (9.7%), Italian (6.1%), and British (4.1%) descent.

There are also significant groups of Swedish (1.5%), Russian (1.5%), French (1.3%), Greek (1.2%), Czech (1.0%), Dutch (1.0%), Lithuanian (0.9%), and Norwegian (0.8%) descent.

The Asian population is ethnically diverse, and includes roughly 87,900 Indians, 61,700 Filipinos, 60,700 Chinese, 35,000 Koreans, 13,700 Vietnamese, and 11,100 Japanese.

[32] Cook County Board chairman John Daley called the wage hike "the moral and right thing to do."

In June 2017, however, nearly 75 home rule municipalities passed measures opting themselves out of the increase.

[34] Since 1932, the majority of its voters have only supported a Republican candidate in a Presidential election three times, all during national Republican landslides–Dwight Eisenhower over native son Adlai Stevenson II in 1952 and 1956, and Richard Nixon over George McGovern in 1972.

The last Republican mayor of Chicago was William Hale "Big Bill" Thompson, who left office in 1931 with a record of corruption.

The most successful Republican candidate for mayor since then was Bernard Epton, who in 1983 came within 3.3 percentage points of defeating Democrat Harold Washington.

To establish more localized government control and policies which reflect the often different values and needs of large suburban sections of the sprawling county, secession movements have been made over the years which called for certain townships or municipalities to form their own independent counties.

In the late 1970s, a movement started which proposed a separation of six northwest suburban townships, Cook County's panhandle (Barrington, Hanover, Palatine, Wheeling, Schaumburg, and Elk Grove) from Cook to form Lincoln County, in honor of the former U.S. president and Illinois resident.

Peloquin argued that the south suburbs are often shunned by the city (although Chicago is not bound or required to do anything for other municipalities) and he blamed the Chicago-centric policies of Cook County for failing to jumpstart the somewhat-depressed south suburban local economy.

Pending sufficient interest from local communities, Peloquin planned a petition drive to place a question regarding the secession on the general election ballot, but the idea was not met with success.

[39] In arguing against the Lincoln County proposal, others noted several of the cities involved had power structures, law enforcement, or de facto "mayors for life" often accused in the press, or civilly or criminally charged with, political corruption, cronyism, and nepotism, and themselves being the main factor in their depressed economies rather than anyone in Cook County government.

The opposition decried that their true reason for joining the secession effort was to start with a 'clean slate' with a new county government by design less willing to enforce responsibility against their abuses of power.

[40][41] Talk of secession from Cook County amongst some outlying communities again heated up in mid-2008 in response to a highly controversial 1% sales tax hike which has pushed the tax rates across the county communities up amongst the highest in the nation.

[43] Construction of the Erie Canal in New York State made a connection from the Atlantic Ocean to the Great Lakes in 1821.

As the Midwest farms proved productive, with much grain to sell to other parts of the US, Chicago and Cook County saw the benefit of a canal to improve the link from the Great Lakes to the Mississippi River.

This canal spurred the growth of Chicago and the areas around it, as water travel was the primary way to ship grain or other commodities in that part of the 19th century.

The two canals and the Great Lakes cemented trade ties between the Midwest and the Northeast, encouraging farmers to grow more than they needed to feed themselves in Illinois, with a large market for grain now open to them.

The Sanitary and Ship Canal was built to serve many aims, including ending using Lake Michigan as a sewer, sending waste water through treatment plants and sending it away from Lake Michigan.

Chicago and the towns along the canal and rivers understood the value of being a hub of a major network.

Rail lines spurred out from Chicago by the 1850s, with major growth in the rail network for freight and passenger transportation coming after the American Civil War, when the transcontinental railroads were completed, coast to coast across the US, stopping in Chicago, the heart of Cook County.

There has been a long running plan for a third major airport to serve the south side of the city and the southern and southwestern suburbs, the Proposed Chicago south suburban airport intended for Peotone, Illinois.

The 29 townships and 2 independent cities of Cook County, with their populations as of the 2010 Census, are:[45] Chicago's eight former townships and annexed parts of others no longer have any governmental structure or responsibility since their annexations, but their names and boundaries are still used on property plats and by Cook County for tax assessment purposes.