Peoria, Illinois, USA is the largest city on the Illinois River and the county seat of Peoria County, Illinois, in the United States. As of the 2000 census, the city had a total population of 112,936. The Greater Peoria Metro area, including suburbs and surrounding, has a population of 370,000. Peoria has become famous as a representation of the average American city because of its demographics and its perceived mainstream Midwestern culture. On the Vaudeville circuit, it was said that if an act would succeed in Peoria, it would work anywhere. The question "Will it play in Peoria?" has now become a metaphor for whether something appeals to the American mainstream public, and Peoria is often used as a test market for new products, services, and public policy polling.

As of the census of 2000, there were 112,936 people, 45,199 households, and 27,345 families residing in the city. The population density was 982.1/km˛ (2,543.4/mi˛). There were 49,125 housing units at an average density of 427.2/km˛ (1,106.3/mi˛). The racial makeup of the city was 69.29% White, 24.79% African American, 0.20% Native American, 2.33% Asian, 0.04% Pacific Islander, 1.20% from other races, and 2.16% from other races. Hispanic or Latino of any race were 2.51% of the population.