Riverside Amusement Park was an amusement park in Indianapolis, Indiana, USA from 1903 to 1970. Originating as a joint venture between engineer/amusement park developer Frederick Ingersoll and Indianapolis businessmen J. Clyde Power, Albert Lieber, and Bert Fiebleman and Emmett Johnson, the park was built by Ingersoll's Pittsburgh Construction Company adjacent to Riverside City Park at West 30th Street between White River and the Central Canal in the Riverside subdivision of Indianapolis.
On 6 January 1903, incorporation papers were filed for Riverside Amusement Company with the State of Indiana. The list of company directors included William Jineson (of Charleroi, Pennsylvania), Elmore E. Gregg and Frederick Ingersoll (both of Pittsburgh, Pennsylvania), J. Clyde Power and Albert Leiber (both of Indianapolis). The following May, the park opened and was an immediate success. One of Ingersoll's signature figure 8 roller coasters was one of several attractions pulling in the crowds in the park's early days; another was a looking-glass maze. The park's first manager, Frank P. Thomas, Sr., decided not to charge an admission fee for entry onto the grounds, opting to charge the patrons by the individual ride (5 cents for the "double-eight tobaggan railway", for example).
Despite Ingersoll's turning his attention away from Riverside Amusement Park and toward his plans for Rocky Glen Park and Indianola Park (with his Luna Parks only two years into the future), Power (himself an engineer) and the directors of the Riverside Amusement Company quickly added an Old Mill ride in which boats were ridden through a darkened tunnel into a replica of a working flour mill. In 1906, J.S. Sandy became the new manager and hired 120 men to expand and update the park. Live entertainment added to the throngs as Sandy arranged for increased streetcar service into the park. On 6 May 1906, opening day for the park's fourth season, approximately 30,000 people visited the park (one-fifth the population of Indianapolis at the time), according to Sandy. Two weeks later, a second competing amusement park, Wonderland, opened its gates to the public. By the end of the year another, White City, opened along the White River, north of the Indianapolis city limit. The three-way rivalry involving Riverside Amusement Park, Wonderland, and White City intensified over the next two years (White City was destroyed by fire 26 June 1908; Wonderland met the same fate three years later).