The organization now known as CT Folk grew out of a folk festival created to raise funds for the Farmington Rail to Trail Association and the CT Fund for the Environment. The first concert, in 1989, featured Tom Paxton, followed in subsequent years by Arlo Guthrie, Judy Collins, Emmy Lou Harris, Odetta, Peter Yarrow. First organized as the Eli Whitney Folk Festival, the name was later changed to the New Haven Folk Festival (with an organizing group called the New Haven Folk Alliance), before becoming CT Folk.
New Haven Folk also started presenting concerts one Friday a month. In 2002 the festival became a 3-day festival, with a Friday night Grassy Hill Song Circle to honor Tom Neff, an early founder and supporter, followed by an all-day festival on Saturday and a Sunday informal song circle. In 2013 the festival was on Saturday only; the Grassy Hill Song Circle was incorporated into the festival, and became a showcase for emerging artists. The informal song circle was discontinued. Concerts were ticketed until 2012, when it became a free festival.
Coleen Campbell spearheaded and directed the Green Expo component of the festival, beginning in 2005, and eventually, the festival itself. Nicole Heriot-Mikula took over as Festival Director in 2016.