Jacob McGavock Dickinson was born on January 30, 1851, in Columbus, Mississippi. By age 14, Dickinson was ready for war when he enlisted as a private in the Confederate cavalry. Dickinson graduated from the University of Nashville in 1871, received his master's degree in 1872, studied law for at Columbia University, and furthered his intellectual activities abroad in Leipzig and Paris. Dickinson was admitted to the Tennessee Bar Association in 1874, became president of the Tennessee Bar Association (1889-1893), served as assistant attorney general of the United States between 1895 and 1897, and became legal counsel for various railroad companies between 1897 and 1909. Additionally, he served as president of the American Bar Association (1907-1908) and assisted in the formation of the American Society of Law.

President William Howard Taft named him secretary of war in March 1909, and Dickinson served in that position until May 1911. Dickinson was nominated for the post over Luke Wright, the popular outgoing secretary in the Roosevelt administration. His nomination was especially surprising considering that Dickinson had been a lifelong Democrat and had pledged to remain one despite his commitment to implement Taft's decisions. While head of the War Department, Dickinson proposed a retirement pension for civil service employees, pressed for admission of foreign students into West Point, and attempted to combat alcoholism and venereal diseases in the military.

Following his time in the cabinet, Dickinson continued to pursue law, representing the Department of Justice as a special assistant attorney general. Jacob Dickinson died on December 13, 1928.