Fairfield is a city in, and the county seat of, Jefferson County, Iowa. It has a population of 9,464 people, according to the 2010 census. It is a Midwestern city surrounded by rolling farmlands filled with corn, soybean, cattle, and hogs with a median family income of $46,138 (10% of families below the poverty line). The city became the county seat in 1839 with 110 residents and grew to 650 by 1847. Its library was established in 1853, and it held its first fair in 1854. Early architecture includes work by George Franklin Barber and Barry Byrne, who trained under Frank Lloyd Wright.
The area now known as Jefferson County was first settled in 1836, and became Jefferson County in 1839, with the new community of Fairfield as the county seat. The name was suggested by Nancy Bonnifield, one of the settlers, because it aptly described the fair fields of the area. But also author Susan Welty suggests it was a play of words on her own name (bonny field). By 1840, Fairfield had a population of 110 and grew to 650 in 1847.