Flimsy cabins and shacks provided rude shelter for many Illinoisans in pioneer days. Later, the balloon-frame house, much cheaper to build than traditional structures, became a trademark of the Prairie State. After a third of Chicago's wooden houses burned in 1871, the city moved to enforce more stringent building codes. The city's predominant dwelling then became the three-or five-story brick apartment house. Great mansions were built in elite areas of Chicago (first Prairie Avenue, later the Gold Coast), and high-rise lakefront luxury apartments first became popular in the 1920s. In the 1970s, Chicago pioneered the conversion of luxury apartment buildings to condominiums, which numbered 242,653 (5.4% of all housing units) in 1990.
In 2002 there were an estimated 4,981,258 housing units in Illinois, of which 4,627,667 were occupied; 67.6% were owneroccupied. About 57.6% of all units were single-family, detached homes. Most units rely on utility gas for heating. It was estimated that 199,427 units were without telephone service, 20,546 lacked complete plumbing facilities, and 22,999 lacked complete kitchen facilities. The average household size was 2.65 people.
In 2002, 60,971 new privately owned units were authorized for construction. The median home value was $147,353. The median monthly cost for mortgage owners was $1,284, while renters paid a median of $665 per month. During 2002, Illinois received over $312.3 million in community planning and development aid from the US Department of Housing and Urban Development.