By July 26, 1881, the desperate young cowboy had put a hundred miles between him and a blood-splattered barroom in Bryan.

Three days of hard riding in the broiling summer heat must have seemed like an eternity to Reuben Stillwell. But with the Brazos County sheriff breathing down his neck, the 21-year-old cowpoke dared not stop.

Never in his worst nightmare could he have imagined Saturday would be the fateful day that changed his life forever. After taking in the horse races with his best buddy Lu...