O.O. Denny Park is named for Orion O. Denny, whose country retreat was once on the property. Denny was the son of Seattle founders, Arthur and Mary Ann Denny. Denny was one of the first students at the Territorial University, where he trained in marine engineering. Denny later became a vice president of the Denny Clay Company in Renton.
When O.O. Denny passed away in 1916, his widow, Helen, donated the 46-acre tract of land to the City of Seattle, with instructions that it be kept as a park named in his honor. In 1922, O.O. Denny Park opened for public use. In 1926, the City of Seattle chose the park as an outdoor camp for Seattle children "who need to experience life in the green forest." In 1968, maintenance of the park was transferred from Seattle to King County. In 2001, after a funding shortfall, the park was slated for closure. On November 5, 2002, nearby Finn Hill residents voted to form the Finn Hill Park and Recreation District to manage the park. Following the annexation of the Finn Hill neighborhood, the City of Kirkland took over managing the park in 2013 though the park is still owned by the City of Seattle.