A Swiss-born park designer and conservationist, Riis was the original superintendent of the Rockford, IL park system from 1912 to 1927. He was also the director of the American Institute of Park Executives from 1923 to 1926, as well as editor and primary writer of the “Conservation of Wild Life” section for Parks and Recreation Magazine for 16 years.

From 1927 to 1932, Riis was instrumental in the design of Allegheny County’s North and South Parks, the first two regional parks outside Pittsburgh, PA. His work was influenced by that of another Midwestern designer, Jens Jensen. Similar to Jensen, he promoted the use of native species and local natural materials to construct such landscape features as a natural stone swimming pool, council rings, waterfalls, and shelters.

Dismissed by the Park Commission in 1932, he returned to the Midwest where he focused on private client work, notably on the estate of Howard Colman in Rockford, IL. He also worked on pioneering deer-browse studies with conservationist Aldo Leopold.