Fairfield is a city in, and the county seat of, Jefferson County, Iowa, United States. It has a population totaling 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.

In 2010, it was named one of six Iowa Great Places. It was named by Smithsonian magazine as one of "The 20 Best Small Towns to Visit in 2013."

The city was the site of the first and second Iowa State Fairs. Fairfield's library was established in 1853, and was the first library in the state of Iowa. It was first housed in a rented room off the city square. Fairfield's library became the first Carnegie Library outside of Pennsylvania or Scotland funded by Andrew Carnegie, who donated $40,000 to build the library.

Early architecture in Fairfield includes Victorian houses designed by George Franklin Barber as well a 1915 house designed by Barry Byrne, who trained under Frank Lloyd Wright. A 1930s bank building was designed in the Streamline Moderne style. Commercial and institutional architecture were influenced by the Louden Industries, including the Louden Foundry. Fairfield is the site of the prototype Carnegie library. This served as the model for 2,700 libraries worldwide.

en.wikipedia.org/wiki/Fairfield,_Iowa