In 1960, Ken Cormier and his wife Violet opened Marvel Drive-In, a drive-in restaurant, next door to a miniature golf course owned by Ken’s brother-in-law, Andre Dallaire. The golf course had been installed the previous year. In 1963, Andre opened a go-kart track behind the golf course, and in 1964 and 1967, Ken added batting cages and an archery range, respectively, behind Marvel Drive-In. Over the next few years, Cormier and Dallaire added several kiddie and carnival-style rides including SkySlides and Swinging Gyms.

In 1967, Cormier and Dallaire formed a partnership and established Funtown USA. Over the next few years, Funtown added a Zipper, bumper cars, and a Bayern Kurve named “Luv Machine”.

In 1996, Cormier bought out the remaining Dallaire interest at the park, and renamed it to Funtown Splashtown USA with the addition of a water park to the property.

The park features a wooden roller coaster called Excalibur, as well as New England's longest and tallest log flume, Thunder Falls. It also has a 220-foot-tall (67 m) drop tower called Dragon's Descent. One of the park's most popular rides is the Astrosphere, an indoor Scrambler which features a laser light show while playing Electric Light Orchestra's "Fire on High".

The Splashtown water park features Pirate's Paradise, a large interactive water playground. For the 2007 season, the water park's size was doubled in an expansion that added two new water slides, Tornado and Mammoth. An additional expansion in 2012 added another six water slides to Splashtown.