According to the United States Census Bureau, the village has a total area of 2.3 square miles (5.9 km²), of which, 2.1 square miles (5.5 km²) of it is land and 0.2 square miles (0.4 km²) of it (6.58%) is water. Most of "Summit" is actually in the floodplain of the Des Plaines River.
There were 3,356 households out of which 38.2% had children under the age of 18 living with them, 48.7% were married couples living together, 15.8% had a female householder with no husband present, and 28.0% were non-families. 23.0% of all households were made up of individuals and 9.7% had someone living alone who was 65 years of age or older. The average household size was 3.16 and the average family size was 3.77.
In the village the population was spread out with 29.2% under the age of 18, 12.1% from 18 to 24, 30.6% from 25 to 44, 17.7% from 45 to 64, and 10.4% who were 65 years of age or older. The median age was 30 years. For every 100 females there were 106.4 males. For every 100 females age 18 and over, there were 105.7 males.
The median income for a household in the village was $38,132, and the median income for a family was $44,063. Males had a median income of $32,287 versus $21,628 for females. The per capita income for the village was $14,611. About 12.6% of families and 16.2% of the population were below the poverty line, including 23.5% of those under age 18 and 11.2% of those age 65 or over.
The National Center for Food Safety and Technology is located adjacent to the Corn Products plant. It is affiliated with the Illinois Institute of Technology and the Food and Drug Administration's Center for Food Safety and Applied Nutrition.