DuPage County (dʒ/) is a county in the U.S. state of Illinois, and one of the collar counties of the Chicago metropolitan area. As of the 2010 census, the population was 916,924, making it Illinois' second-most populous county. Its county seat is Wheaton. DuPage County has become mostly developed and suburbanized, although some pockets of farmland remain in the county's western and northern parts. The county has a high socioeconomic profile and residents of Hinsdale, Naperville and Oak Brook include some of the wealthiest people in the Midwest. On the whole, the county enjoys above average median household income levels and low overall poverty levels when compared to the national average. In 2018 Niche ranked two DuPage municipalities (Clarendon Hills #3 and Naperville #16) amongst the top 20 best places to live in America.
DuPage County was formed on February 9, 1839 out of Cook County. The county took its name from the DuPage River, which was, in turn, named after a French fur trapper, DuPage. The first written history to address the name, the 1882 History of DuPage County, Illinois, by Rufus Blanchard, relates:
The DuPage River had, from time immemorial, been a stream well known. It took its name from a French trader who settled on this stream below the fork previous to 1800. Hon. H. W. Blodgett, of Waukegan, informs the writer that J. B. Beaubien had often spoken to him of the old Frenchman, Du Page, whose station was on the bank of the river, down toward its mouth, and stated that the river took its name from him. The county name must have the same origin. Col Gurden S. Hubbard, who came into the country in 1818, informs the writer that the name DuPage, as applied to the river then, was universally known, but the trader for whom it was named lived there before his time. Mr. Beaubien says it is pronounced Du Pazhe (a having the sound of ah, and that the P should be a capital). This was in reply to Mr. Blodgett’s inquiry of him concerning the matter.
The first white settler in DuPage County was Bailey Hobson, who, with Lewis Stewart, built a house in 1831 for the Hobson family at a site about 2 miles south of present-day downtown Naperville. Hobson later built a mill to serve surrounding farmers. Today, the Hobson house still stands on Hobson Road in Naperville, and the location of the mill is commemorated with a millstone and monument in today's Pioneer Park.
According to the U.S. Census Bureau, the county has a total area of 336 square miles (870 km2), of which 327 square miles (850 km2) is land and 8.9 square miles (23 km2) (2.6%) is water. The DuPage River and the Salt Creek flow through DuPage County. According to the Forest Preserve District of DuPage County, the highest point in the county is located at the Mallard Lake Landfill, which at its highest point is 982 feet (299 m) above mean sea level.
In recent years, average temperatures in the county seat of Wheaton have ranged from a low of 14 °F (−10 °C) in January to a high of 87 °F (31 °C) in July, although a record low of −26 °F (−32 °C) was recorded in January 1985 and a record high of 105 °F (41 °C) was recorded in July 1995. Average monthly precipitation ranged from 1.56 inches (40 mm) in February to 4.60 inches (117 mm) in August.
DuPage County has become more diverse. The population of foreign-born residents increased from about 71,300 in 1990 to 171,000 by 2009 estimates.
There were 325,601 households, out of which 37.00% had children under the age of 18 living with them, 60.90% were married couples living together, 7.90% had a female householder with no husband present and 28.00% were non-families. 22.90% of all households were made up of individuals and 6.80% had someone living alone who was 65 years of age or older. The average household size was 2.73 and the average family size was 3.27.
In the county, the population was spread out with 26.70% under the age of 18, 8.20% from 18 to 24, 32.40% from 25 to 44, 22.80% from 45 to 64 and 9.80% who were 65 years of age or older. The median age was 35 years. For every 100 females, there were 97.20 males. For every 100 females, age 18 and over, there were 94.20 males.
The median income for a household in the county was $98,441 and the median income for a family was $113,086. Males had a median income of $60,909 versus $41,346 for females. The mean or average income for a family in DuPage County is $121,009, according to the 2005 census. The per capita income for the county was $38,458. About 2.40% of families and 3.60% of the population were below the poverty line, including 3.90% of those under age 18 and 4.30% of those age 65 or over.
Fermilab, which has the world's second-highest-energy particle accelerator, is in Batavia, where it straddles the border between Kane and DuPage counties.Argonne National Laboratory, one of the United States government's oldest and largest science and engineering research laboratories, is in unincorporated, southeast DuPage County. Both laboratories conduct tours of their facilities.
The powers of the County Board include managing county funds and business, levying taxes, and appropriating funds. The County Board exercises powers not assigned to other elected officials or other boards.
The county is divided into six districts. Each district elects three members to the County Board in staggered two-year and four-year terms. The Chairman of the County Board is the chief executive officer of DuPage County, and is elected countywide every four years.
The County Board is controlled by the Republican Party by an 11 to 7 margin.
While many suburban counties outside large cities have trended Democratic in presidential years since the 1990s DuPage County remains a stronghold of the Republican Party, and is reckoned a classic bastion of suburban conservatism. The county continues to lean Republican in state and local politics, however in the 2018 Illinois gubernatorial election, J. B. Pritzker became the first Democratic candidate for the governorship to win the county in more than 100 years.
The county supported Barack Obama, a Chicago resident, in 2008 and 2012 (albeit narrowly in 2012). Obama was the first Democratic presidential nominee to win the county since Franklin Pierce in 1852. The only time prior to 2008 that a Republican had failed to win the county was in 1912, when the GOP was mortally divided and former President and Progressive Party nominee Theodore Roosevelt won over half the county's vote.
In the U.S. House of Representatives, DuPage County is in the 5th, 6th, 8th, 11th and 14th districts. In the 2018 general election, despite the county's historical Republican dominance, Democrats won every congressional district within the county.
Republicans historically controlled local politics in DuPage County from the nineteenth century until modern times. Democrats have only held countywide office twice. In 1934 William Robinson was elected Circuit Clerk and Arthur Hellyer was elected Treasurer. That year also saw the only Democratic majority county board in DuPage history. Robinson and Hellyer each served one term; Robinson lost his bid for a full term in 1936 and Hellyer left the Treasurer's office to make a failed bid for probate judge in 1938. In 2018, as part of a larger suburban realignment, Democratic candidate Jean Kaczmarek won the election for County Clerk and Daniel Hebreard won the President of the Forest Preserve District of DuPage County.
During that same period Democrats were sporadically elected at the county board township levels. In 1972, Don Carroll was elected to the County Board. In the Democratic wave of 1974, Jane Spirgel, Mary Eleanor Wall, and Elaine Libovicz were elected. All four were from the northeastern portion of DuPage, which at that time was the most Democratic. Republicans regained all seats on the board when Jane Spirgel ran for Illinois Secretary of State with Adlai Stevenson III under the Solidarity Party banner. In 2000, Linda J. Bourke Hilbert was elected. Like her 1970s counterparts, she was from the northeastern portion of the county. During the 2008 Democratic wave, three Democrats were elected to the board. After the initial Obama wave, Republicans reasserted themselves on the board and by 2017 Democrats held only one of the eighteen board seats. In the 2018 general election, Democrats won seven seats as well as the offices of County Clerk and Forest Preserve District President.
The DuPage County Regional Office of Education provides regulatory and compliance oversight, quality services and support, and a variety of other services and information to the public schools within the forty-two school districts of the county that provide education to over 161,000 students in 245 schools.
North–south roads (from west to east) include: IL 59 (Sutton Road), IL 53 (Rohlwing Road), I-355 (Veterans Memorial Tollway) and IL 83 (Kingery Highway). East–west roads (from south to north) include: I-55 (Stevenson Expressway) I-88 (Ronald Reagan Memorial Tollway), US 34 (Ogden Avenue), IL 56 (Butterfield Road), IL 38 (Roosevelt Road), IL 64 (North Avenue), Army Trail Road, US 20 (Lake Street), IL 19 (Irving Park Road) and IL 390 (Elgin–O'Hare Expressway), which begins at the Thorndale Avenue exit on I-290 and ends on Lake Street, in Hanover Park. I-294 partially enters DuPage County on its eastern border between Westchester, in Cook County, and Oak Brook, in DuPage County. Only the southbound lanes enter the county though.