The collar counties are the five counties of Illinois

Illinois

Illinois is the fifth-most populous state of the United States of America, and is often noted for being a microcosm of the entire country. With Chicago in the northeast, small industrial cities and great agricultural productivity in central and northern Illinois, and natural resources like coal,...

 that border on Chicago

Chicago

Chicago is the largest city in the US state of Illinois. With nearly 2.7 million residents, it is the most populous city in the Midwestern United States and the third most populous in the US, after New York City and Los Angeles...

's Cook County

Cook County, Illinois

Cook County is a county in the U.S. state of Illinois, with its county seat in Chicago. It is the second most populous county in the United States after Los Angeles County. The county has 5,194,675 residents, which is 40.5 percent of all Illinois residents. Cook County's population is larger than...

. The collar counties (DuPage

DuPage County, Illinois

As of the 2010 Census, the population of the county was 916,924, White Americans made up 77.9% of Dupage County's population; non-Hispanic whites represented 70.5% of the population. Black Americans made up 4.6% of the population. Native Americans made up 0.3% of Dupage County's population...

, Kane

Kane County, Illinois

Kane County is a county located in the U.S. state of Illinois. According to the 2010 census, it has a population of 515,269, which is an increase of 27.5% from 404,119 in 2000. Its county seat is Geneva, and its largest city is Aurora.- Geography :...

, Lake

Lake County, Illinois

Lake County is a county in the northeastern corner of the state of Illinois, on the shore of Lake Michigan. According to the 2010 census, it has a population of 703,462, which is an increase of 9.2% from 644,356 in 2000. Its county seat is Waukegan. The county is part of the Chicago metropolitan area...

, McHenry

McHenry County, Illinois

McHenry County is a county located in the U.S. state of Illinois. According to the 2010 census, it has a population of 308,760, which is an increase of 18.7% from 260,077 in 2000. Its county seat is Woodstock. This county is part of the Chicago metropolitan area. It is the sixth largest county, in...

, and Will

Will County, Illinois

As of the census of 2000, there were 502,266 people, 167,542 households, and 131,017 families residing in the county. The population density was 600 people per square mile . There were 175,524 housing units at an average density of 210 per square mile...

) are tied to Chicago economically, but, like many suburb

Suburb

The word suburb mostly refers to a residential area, either existing as part of a city or as a separate residential community within commuting distance of a city . Some suburbs have a degree of administrative autonomy, and most have lower population density than inner city neighborhoods...

an areas in the United States, have very different political leanings than does the core city. Chicago has long been a Democratic

Democratic Party (United States)

The Democratic Party is one of two major contemporary political parties in the United States, along with the Republican Party. The party's socially liberal and progressive platform is largely considered center-left in the U.S. political spectrum. The party has the lengthiest record of continuous...

 stronghold, and the collar counties are known for their slightly Republican leanings.

While the demographics of these suburban Chicago counties are fairly typical for American metropolitan area

Metropolitan area

The term metropolitan area refers to a region consisting of a densely populated urban core and its less-populated surrounding territories, sharing industry, infrastructure, and housing. A metropolitan area usually encompasses multiple jurisdictions and municipalities: neighborhoods, townships,...

s, the term is apparently unique to this area. And because Chicago is so firmly entrenched in the Democratic column, and rural Downstate is so overwhelmingly Republican

Republican Party (United States)

The Republican Party is one of the two major contemporary political parties in the United States, along with the Democratic Party. Founded by anti-slavery expansion activists in 1854, it is often called the GOP . The party's platform generally reflects American conservatism in the U.S...

, the collar counties are routinely cited as being the key to any statewide election.

While the term is perhaps most often employed in political discussions, that is not its exclusive use. Barack Obama

Barack Obama

Barack Hussein Obama II is the 44th and current President of the United States. He is the first African American to hold the office. Obama previously served as a United States Senator from Illinois, from January 2005 until he resigned following his victory in the 2008 presidential election.Born in...

used the term in his speech before the Democratic National Convention in 2004.