The legend of St. Urho was the invention of a Finnish-American named Richard Mattson, who worked at Ketola's Department Store in Virginia, Minnesota in spring of 1956. Mattson later recounted that he invented St. Urho when he was questioned by coworker Gene McCavic about the Finns' lack of a saint like the Irish St. Patrick, whose feat of casting the snakes out of Ireland is remembered on St. Patrick's Day. In fact, the patron saint of Finland is Henry (Bishop of Finland).
According to the original "Ode to St. Urho" written by Gene McCavic and Richard Mattson, St. Urho was supposed to have cast "tose 'Rogs" (those frogs) out of Finland by the power of his loud voice, which he obtained by drinking "feelia sour" (sour whole milk) and eating "kala mojakka" (fish soup).
The original "Ode to St. Urho" identified St. Urho's Day as taking place on May 24. Later the date was changed to March 16, the day before St. Patrick's Day. St. Urho's feast is supposed to be celebrated by wearing the colors Royal Purple and Nile Green. Other details of the invented legend also changed, apparently under the influence of Dr. Sulo Havumäki, a psychology professor at Bemidji State College in Bemidji, Minnesota. The legend now states that St. Urho drove away grasshoppers (rather than frogs) from Finland using the incantation "Heinäsirkka, heinäsirkka, mene täältä hiiteen!" ("Grasshopper, grasshopper, go from hence to Hell!"), thus saving the Finnish grape crops.
The modern celebration of St Urho's day was created by Brian Kirchberg of Chippewa Falls, Wisconsin. Kirchberg, a high school teacher, was teaching in the Upper Peninsula of Michigan in the early to mid 1950's in an area populated largely by people of Finnish heritage. He and his friends contocted March 16 as St Urho's day so that they had two days to celebrate, the next day being St. Patrick's Day.  The designation of St Urho as patron saint of the Finnish is particularly humorous because 82.5% of the Finnish population is affiliated with the Lutheran Church, which does not recognize the Feasts of Saints. Brist promoted the "annual cancellation" of the St Urho's Day Parade in Chippewa Falls, Wisconsin with advertisements in the Chippewa Herald Telegram and by teaching his high school students about the legend of St Urho 
The "Ode to St. Urho" has been modified to reflect these changes in the feast day and legend. The Ode is written in a self-parodying form of English as spoken by Finnish immigrants. There is also a "Ballad of St. Urho" written by Sally Karttunen.
The selection of the name Urho as the saint's name was probably influenced by the accession of Urho Kekkonen to the presidency of Finland in 1956. Urho in the Finnish language also has the meaning of hero or simply brave.
There are St. Urho fan clubs in Canada and Finland as well as the U.S., and the festival is celebrated on March 16 in many American and Canadian communities with Finnish roots. The original statue of St. Urho is located in Menahga, Minnesota. Another interesting chainsaw-carved St. Urho statue is located in Finland, Minnesota. There is a beer restaurant called St. Urho's Pub in central Helsinki, Finland. A 2001 book, The Legend of St. Urho by Joanne Asala, presents much of the folklore surrounding St. Urho and includes an essay by Richard Mattson on the "birth" of St. Urho.