Lindley Garrison was born on November 28, 1864, in Camden, New Jersey. He was educated at public schools in Philadelphia, as well as at Episcopal Academy and Exeter, before spending a year at Harvard University in 1885. Garrison studied law at the Philadelphia law offices of Redding, Jones, & Carson, while earning a law degree from the University of Pennsylvania in 1886. Garrison practiced law in New Jersey, becoming a senior partner in the Jersey City firm of Garrison, McManus, & Enright in 1899. Moving to the public sector in 1904, Garrison became the youngest lawyer in history to be appointed vice chancellor of New Jersey.
He entered the cabinet of President Woodrow Wilson in 1913, serving as secretary of war until February 1916. During his tenure, he had to contend with hostilities involving Mexico, as well as ensuring the nation's military preparedness while Europe plunged into war. He resigned his post due to conflicts with the President. Garrison returned to the practice of law following his time in Wilson's cabinet and was appointed to the receivership of the Brooklyn Rapid Transit Company until 1923. He died in Seabright, New Jersey, on October 19, 1932.