The son of an architect, Kreis was apprenticed in his youth to a stonecarver in his native Essen from 1915 to 1919. He also studied at the School of Applied Art there and at the State Art School in Munich from 1920 to 1923 under Paul Wackerle. He came to the United States in the latter year and continued his education at the Beaux Arts Institute of Design in New York while working as an assistant to Paul Manship and to C. Paul Jennewein.
Among Kreis's many public sculptures are the following: The Birth of a Nation, a monument for Fairmount Park, Philadelphia; a huge marble figure for the Bronx Post Office, New York; two large bronze figures of soldiers for the lobby of the War Department Building, Washington; two aluminium figures for the lobby of the Federal Court House, Erie, Pennsylvania; granite reliefs for the Social Services Building, Washington; and a war memorial for the Virginia Polytechnic Institute. He has also designed a number of medals including the official medal of the 1939 New York World's Fair and the Medal of Honor of the National Sculpture Society. His allegorical works Indian Summer and In Pensive Mood are in New York at the Metropolitan Museum of Art and the Whitney Museum of American Art respectively. He won the National Academy's Watrous Gold Medal twice, once in 1951 for his stone sculpture, Descent from Calvary, and again in 1954 for Karen.
