This postcard advertises the 1917 Saint Paul Outdoor Sports Carnival, one of the earlier versions of the St. Paul Winter Carnival. The first carnivals were held from 1886 to 1888 and 1896. They were again held in 1916 and 1917 and from 1937 to 1942. The Winter Carnival has been held annually since 1946.
Many pictures, including the 1917 ice palace, can be seen on an unofficial Winter Carnival website. That website also has links to other known St. Paul Winter Carnival websites.