Save the dates - April 19 & 20! Visit the World's Oldest Annual Invention Convention! Adult & student inventors test market their new products. Inventions for sale. Souvenir Gift Shop. Concession Stand. Spend a few hours, or the day, in the beautiful Minnesota River Valley. 26th Annual Minnesota Student Inventors Congress event. Daktronics presents: Pixel Power: More Than a Trillion at 10:30 and 1:30 daily. Suntava Purple Corn presents Purple Corn as a Superfood at 11:30 daily.