It's 1954, and a young Ohio farmer named John Snoddy walks out of an auction barn with a gangly, too-leggy heifer that cost him $375—every cent he made selling market hogs that fall. His neighbors laugh. His wife hopes they haven't wasted the pig money. The heifer doesn't look like much of anything.

Seven years later, a man named Dick Brooks sees that heifer's daughter walking over a hillside in West Salem, Ohio, and refuses to leave until she's his. Fifteen years after that, her genetics are flowing into virtually every Holstein herd in North America through a bull calf that sold for a "disappointing" $9,000—a calf who became the most-proven sire in U.S. history.

This is the story of Harborcrest Rose Milly, the three-time All-American who scored 97 points when that number meant something almost impossible. But more than that, it's th ...