The former granite Ronde island, which the extension was made around, was destroyed by blasting and the resulting crater it left turned into Dolphin lake, which the park surrounds.

Public transit provides accessibility by means of the island's Metro station with seasonal shuttle bus service to the park.

In 1967, La Ronde was built as the entertainment complex for Expo 67, the world fair held in Montreal from April 28 to October 29, 1967.

[7] In 1973, in October, the rapid transit train system that served La Ronde, the Expo Express, permanently closed.

Its terminus station sat right above La Ronde's main entrance, and brought off-island visitors directly to the park during Expo 67 and the early days of Man and His World.

In 1979, on July 8, the drowning deaths of three people occurred at La Ronde's Dolphin Lake when "The Mississippi" tour boat, ferrying up to 60 passengers, capsized.

[8] Two weeks later, on July 22, a fourth drowning death occurred when a man attempted a swim across Dolphin Lake at late-night, after the park had closed.

The episode featured the park's giant roller coaster, haunted house with a dragon on the front and its old-fashioned carousel.

In 2001, the City of Montreal sold La Ronde to Six Flags, an American theme park chain, in a deal completed on May 4, 2001.

Before the announcement of the Six Flags purchase, the city had considered offers from other bidders including Paramount Parks, Cedar Fair, and Parc Astérix.

In May 2002, La Ronde announced the installation of a Bolliger & Mabillard inverted roller coaster called Le Vampire, which was the first major investment by Six Flags.

In 2003, La Ronde opened six new rides including Auto Tamponneuses, Tour de Ville, Manitou, Vertigo, Grand Carrousel, and Toboggan Nordique.

The roller coaster, which opened in 1999 at Six Flags AstroWorld, was installed over the Lac des Dauphins at the park for the 2010 season and is named Ednör – L'Attaque.

[56] It features special effects and is themed around an alleged sea monster that was purported to have appeared in the Lac des Dauphins.

On Saturday, May 19, 2018, Six Flags La Ronde opened a platform thrill ride called Le Tourbillon, a Larson International GX5 model (Waltzer-style) Tilt-A-Whirl, residing along L'Avenue across from the Phoenix.

In November 2022, La Ronde began the demolition and removal of the Minirail, another original ride dating back to Expo 67.

[64] In May 2023, La Ronde silently retired its Galopant carousel (built in 1885) when it was removed from its official park map and list of rides.

The carousel has been at La Ronde since Expo 67, but heritage groups are concerned as its upkeep and maintenance have been abandoned and its now in a deteriorating state.