The town was founded in 1855 when John Carson, his four brothers, and others settled in the Cedar Valley. The settlement was soon known as Frogtown. The population ballooned after the arrival of Johnston’s Army in 1858-59, sent to Utah to suppress the rumored rebellion there. The army established a nearby camp called Camp Floyd, and the population grew to over 7,000, including 3,500 troops (nearly one-third of the entire U.S. Army at that time), teamsters, gamblers, and camp followers of various persuasions. With no rebellion taking place, the troops were recalled in 1861, sent east to fight for the Union with the outbreak of the Civil War.
Frogtown became Fairfield in 1861, named after Amos Fielding, who had participated in establishing the community.
The Stagecoach Inn, located in Fairfield and now a museum, was used by travelers passing through via stage coach, military personnel, and riders on the Pony Express trail.
Here’s a good blog post on Fairfield, http://bonnevillemariner.wordpress.com/2010/01/25/1159/
Visit my list of places in Utah.