Background knowledge of germplasm helps corn (Zea mays L.) breeders develop inbreds and predict hybrids. The background of 'Minnesota 13' is still not generally understood. We provide an explanation for the mystery and provide conclusive evidence for Minnesota 13's origin from plant breeding records at the University of Minnesota, whose archives contain corn breeding nursery books. We also cite Minnesota Agriculture Experiment Station annual reports, bulletins, and other pertinent sources. A seed lot collected in 1888 designated as University No. 13 and reported as being improved by Prof. Willet Hays and Andrew Boss in an 1890 bulletin was later destroyed by a seed house fire. They collected a new seed lot in 1893 and the same designation, No. 13, was again used. We show that this second seed lot was common corn grown in the St. Paul, MN, area. We also review the improvement of Minnesota 13 and its influence on the history of corn growing in Minnesota, Wisconsin, and France. We diagram and discuss the background of Pioneer Hi-Bred Inbred PH207 and the importance of Minnesota 13 as 13% of the documented background of U.S. hybrid corn.