Violence dictated the daily rhythms of Cole Younger's life. During the Civil War he was selected to join Quantrill's Raiders because he owned his own revolver. His participation in the brutal 1863 raid on Lawrence, Kansas, drove him and other guerrillas into hiding as Union troops sought to punish the perpetrators of atrocities including the murder of women and children. Younger met up with Jesse James in 1866. The James and Younger families cooperated in a series of bank and train robberies over the next decade that led to a feeling of invincibility. That feeling came to an end in...