Fairfield is a very small city located in the state of Illinois. With a population of 4,779 people and two associated neighborhoods, Fairfield is the 348th largest community in Illinois.

The citizens of Fairfield are slightly less educated than the national average of 21.84% for the average city or town: 16.58% of adults in Fairfield have a bachelor's degree or advanced degree

The per capita income in Fairfield in 2022 was $28,769, which is lower middle income relative to Illinois and the nation. This equates to an annual income of $115,076 for a family of four. However, Fairfield contains both very wealthy and poor people as well.

The people who call Fairfield home describe themselves as belonging to a variety of racial and ethnic groups. The greatest number of Fairfield residents report their race to be White, followed by Black or African-American. Important ancestries of people in Fairfield include English, German, Irish, Swedish, and Scottish.

The most common language spoken in Fairfield is English. Other important languages spoken here include Spanish and Polish.