Born on April 19, 1821 (commonly mistakenly reported as 1831), in Ithaca, New York, Leggett's parents were members of the Society of Friends. In 1837, at sixteen years of age, Leggett moved with his parents to Geauga County, Ohio, where he helped his family establish a farm.
Born on April 19, 1821 (commonly mistakenly reported as 1831), in Ithaca, New York, Leggett's parents were members of the Society of Friends. In 1837, at sixteen years of age, Leggett moved with his parents to Geauga County, Ohio, where he helped his family establish a farm. Leggett rarely attended school, receiving the bulk of his education from his parents. He held his parents' Quaker beliefs but forsook them with the American Civil War's outbreak. As an adult, Leggett strongly supported education, becoming the first superintendent of the Akron, Ohio public school system in 1847. He left this position in 1849 due to a salary dispute. Having passed the Ohio bar exam in 1843, Leggett now became a lawyer in Warren, Ohio, opening his own practice. He also sometimes taught in the Warren public schools. In 1855, he joined the faculty of the Ohio College of Law in Poland, Ohio. In 1858, Leggett became the superintendent of public schools in Zanesville, Ohio, a position he held until the Civil War's eruption.
In December 1861, Leggett enlisted in the Union Army, becoming a lieutenant colonel in the Seventy-Eighth Regiment Ohio Volunteer Infantry. He received his commission on December 18, 1861, and on January 11, 1862, military authorities promoted him to the rank of colonel in this same regiment. He led the Seventy-Eighth Ohio into battle at Fort Donelson in February 1862. He also participated in the Battle of Shiloh, Tennessee and the Siege of Corinth, Mississippi. At Shiloh, Confederate soldiers managed to wound Leggett. On May 16, during the Siege of Corinth, Confederate soldiers shot Leggett's horse, causing the colonel to fall and to sustain minor injuries. Following the capture of Corinth, Leggett then advanced upon Jackson, Tennessee, where the Seventy-Eighth Ohio captured practically the entire Confederate garrison, as well as a large amount of supplies. During the remainder of 1862, Leggett's command remained primarily in northern Mississippi and western Tennessee, where on August 30, 1862, Leggett's men successfully defended Bolivar, Tennessee from Confederate attack. In this battle, Confederate forces again wounded Leggett. Military officials promoted Leggett to the rank of brigadier general on November 29, 1862.
During the first months of 1863, Leggett's command participated in the Vicksburg Campaign. Confederate forces wounded Leggett at the Battle of Champions Hill and twice more at the Battle of Fort Hill. Following the Union Army's capture of Vicksburg, Mississippi, Leggett assumed command of the Third Division, Seventeenth Corps. He led this division for the remainder of the war, participating in Union General William T. Sherman's Atlanta Campaign and the March to the Sea in 1864 and his Carolinas Campaign of 1865. Military officials promoted Leggett to the rank of brevet major general on July 22, 1864, and then to the full rank of major general on January 15, 1865. Upon the war's conclusion, Leggett resigned from the army on July 22, 1865, but officials did not formally accept his resignation until November 1, 1865.
Following the conflict, Leggett returned to Zanesville, where he practiced the law. In 1871, President Ulysses S. Grant appointed Leggett as a United States patent Commissioner. Upon leaving this office, Leggett moved to Cleveland, Ohio, where he resumed his legal practice. He died in Cleveland on April 26, 1896. Leggett was buried in Cleveland's Lakeview Cemetery.