Oak Park is located immediately west of Chicago. The boundary between the two municipalities is Austin Boulevard on the east side of Oak Park and North Avenue on the village's north side. Oak Park also borders Cicero along its southern border, Roosevelt Road, from Austin to Lombard; and Berwyn from Lombard to Harlem. Harlem also serves as its western border, where between Roosevelt and South Blvd, it borders Forest Park and between North Blvd and North Ave to the west it borders River Forest.
The entire village of Oak Park lies on the shore of ancient Lake Chicago, which covered most of the city of Chicago during the last Ice Age and is today called Lake Michigan. Ridgeland Avenue in eastern Oak Park marks the shoreline of the lake, and was once an actual ridge. One of North America's four continental divides runs through Oak Park. This divide, a slight rise running north-south through the village, separates the St. Lawrence River watershed from the Mississippi River watershed, and is marked by a plaque on Lake Street at Forest Avenue.
According to the United States Census Bureau, the village has a total area of 4.7 square miles (12.2 km²). None of it is covered by water.
As of the census of 2000, there were 52,524 people, 23,079 households, and 12,970 families residing in the village. The population density was 11,173.4 people per square mile (4,314.8/km²). There were 23,723 housing units at an average density of 5,046.6/sq mi (1,948.8/km²). The racial makeup of the village was 68.78% White, 22.44% African American, 0.15% Native American, 4.15% Asian, 0.03% Pacific Islander, 1.63% from other races, and 2.82% from two or more races. Hispanic or Latino of any race were 4.52% of the population. 14.5% were of Irish, 11.3% German, 6.8% Italian and 5.5% English ancestry according to Census 2000. 88.1% spoke English and 4.2% Spanish as their first language.
There were 23,079 households, out of which 29.5% had children under the age of 18 living with them, 42.1% were married couples living together, 11.6% had a female householder with no husband present, and 43.8% were non-families. 37.0% of all households were made up of individuals and 8.6% had someone living alone who was 65 years of age or older. The average household size was 2.26 and the average family size was 3.06.
In the village the population was spread out with 24.2% under the age of 18, 6.7% from 18 to 24, 35.2% from 25 to 44, 24.4% from 45 to 64, and 9.5% who were 65 years of age or older. The median age was 36 years. For every 100 females there were 86.9 males. For every 100 females age 18 and over, there were 82.2 males.
The median income for a household in the village was $59,183, and the median income for a family was $81,703. Males had a median income of $51,807 versus $40,847 for females. The per capita income for the village was $36,340. About 3.6% of families and 5.6% of the population were below the poverty line, including 5.8% of those under age 18 and 7.9% of those age 65 or over.
Oak Park has a long history of encouraging and maintaining racial and ethnic diversity, much of which was started in conjunction with the 1966 Chicago Open Housing Movement. The village operates a Diversity Assurance Program within its housing programs department to ensure a stable, diverse, and integrated population. Years ago, Oak Park eliminated the use of "For Sale" signs in front of houses, widely considered one of the keys of success to maintaining the high diversity.
