Early Life and Education
At the age of 10, his family moved to Franklin Co. Tennessee and joined other family members who had migrated into this area. At age 17, A. P. Stewart was appointed to the West Point Military Academy in 1838.  His classmates included many famous leaders of the civil war including Longstreet (his roommate), D.H. Hill, Van Dorn, MacLaws, Manfield Lovell, Richard Anderson, G.W. Smith, John Newton, George Sykes, Seth Williams, John Pope and William Rosecrans.  Stewart graduated 12th in his class at West Point and was commissioned a Lieutenant of Artillery.  He continued on at West Point as an instructor in Mathematics but he resigned from the Army in 1845.  In the same year, he accepted a teaching position at Cumberland University in Lebanon, Tennessee and married Harriet Chase of Connecticut (whom he met on a visit there). He always considered Lebanon his home.

The Restless Years (1849 - 1861)
In 1849, he took a teaching position at University of Nashville but returned to Cumberland University in 1850. He refused a teaching position at VMI which Stonewall Jackson was ultimately  to hold. In 1854, he returned to University of Nashville but went back to Cumberland in 1856 after turning down positions at Washington University in St. Louis and the University of Mississippi. At Cumberland, he helped organize the first college chapter of the YWCA.

Civil War Experiences
A. P. Stewart was opposed to the succession of Tennessee at the beginning of the Civil War. Neither he nor his family had ever owned slaves.  However when war came he volunteered in May of 1861 into the Provisional Army of Tennessee and was commissioned a Major of Artillery and was mustered into the Confederate Army in 1861.

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Map showing Mississippi River and the locations of Island No. 10, Tn.; Ft. Pillow, Tn.; Columbus, Ky.;  New Madrid, Mo. and Corinth, Ms.		A.P. Stewart's first assignment was to Island No. 10 on the Mississippi River (see map) which was under the command of General Gideon Pillow. By order of General Polk, made at the earnest personal solicitation of Governor Jackson, who had gone to Memphis for that purpose, General Pillow moved into Missouri from Tennessee, with 12,000 men, and occupied New Madrid, Missouri on the 28th of July, with intent to unite in the effort to repossess the state. General A.S. Johnston wanted Stewart to take command of the forces at Columbus, Kentucky and he recommended that Stewart be promoted to the rank of Brigadier General however to recommendation was denied.  Stewart was placed in charge of artillery at Columbus including the huge gun nicknamed "The Lady Polk" and was able to stop the advance of Grant at Columbus.   When General Bragg arrived from the Gulf Coast he began to concentrate his troops around the town of Corinth, Mississippi. At Corinth, Stewart's Brigade was brought to full status  and he and his men were placed in General Polk's Corp. During the Battle of Shiloh Church, General A.S. Johnston detached Stewart's Brigade to support General Bragg on the first day of the Battle. Stewart was criticized for his failure to keep control of his men at the Hornet's Nest.  This in part was due to contradictory orders from Generals Bragg and Polk

Stewart was then attached to General Chetham Division and during the Kentucky Campaign he was complimented for helping support the attack on the Federal left at Perryville, Kentucky. Later at Stone's River, Georgia, Steward first showed his true ability to handle troops as he helped to drive General Sheridan from his position. Stewart appeared to do well in battle when he was allowed to command without the influence of superior officers. Shortly after, Stewart's troops began calling him "Old Straight" out of respect for his command.

In June of 1863, Stewart was promoted  to Major General and given a newly organized Division and this division along with Cleburne's made up General Hardee's Corp. He fought at Hoover's Gap and Tullahoma, Tennessee and in both instances did not distinguish himself due to receiving conflicting orders from superiors. In September before Chickamauga, he joined Buckner's Corp.  D.H. Hill of Cleburne's Division said of the Battle of Chickamauga that, "It was desultory fighting from right to left, without concert, and at inopportune times. It was the sparring of the amateur boxer, and not the crushing blows of the trained pugilist." On the first day of the battle, Stewart was able to help break the Federal center but was later overwhelmed by new divisions put in the field by the federals. The three confederate Divisions  met with initial success but the were driven into retreat by six federal Divisions.  Stewart was able to help exploit Longstreet's success on the second day.  Chickamauga was the first of two major battles whose ultimate goal was to maneuver Bragg out of Tennessee. After Chickamauga, much criticism of  was heaped upon General Bragg by his staff.  It was believed that Bragg including: 1) his lack of the knowledge of the situation and 2) lack of personal execution of his orders.  Bragg had no well-organized system of independent scouts as Lee had. Instead Bragg in part depended upon local Negroes with "changed hearts" for his information on the enemy.  Bragg appeared to be constantly uncertain of the position or strength of the enemy and appeared to be bewildered by "the popping out of the rats from so many holes."  A.P. Stewart made no such criticism of Bragg and refused to sign an anti-Bragg petition being circulated by his staff.

Following the defeat of Rosecrans' army at Chickamauga, the Army of Tennessee was revamped and reorganized before the Federal strategy's next great engagement, Chattanooga.  Bragg at once took strong positions on Missionary Ridge and Lookout Mountain.  From these heights he was able to besiege the entire Army of the Cumberland in Chattanooga and obstruct the main arteries of supply to the Federal troops. Stewart was assigned to Breckinridge's Corp and during the Battle of Chattanooga was assigned with Anderson and Bates to hold Missionary Ridge. Stewart felt that he did not have enough men to adequately defend his portion of the ridge.  Stewart was badly defeated at Missionary ridge and lost one third of his division defending it.

After Chattanooga, Joe Johnston took command of the Army and Stewart was moved to Hood's Corp.  At Resaca, Stewart was repulsed but did good work at New Hope Church.   General Polk is killed on June 14, 1863 at Kennesaw Mountain and Stewart is promoted to Lieutenant General and assumes command of the Army of Mississippi which later was to become a Corp of the Army of Tennessee. Hood is placed in command of the Army of Tennessee. Stewart was wounded at the Battle of Ezra Church and was taken to Savanna but he returned to his command after a couple of weeks. During the Battle of Jonesboro,  During the final months of the war, Stewart helped hold the city of Atlanta. Hardee is sent to command the defense of Savanna and Cheatum is given command of Hardee's Corp. Stewart took part in the last campaigns in Tennessee. During the Battle of Spring Hill, his orders change several times and he is criticized by Hood for being ineffective.  Stewart is also in the thick of the Battle of Franklin.  After the battle, Steward become the de facto leader of the Army of Tennessee when it retreated and he was ultimately given that command.  He fought at the Battle of Bentonville, Arkansas and commanded the center of the battle and was complimented for performing well under the circumstances.  His army had dwindled down to an effective force of 5,175 men and he surrendered the army to Labaron in late June or early July, 1865.

Post Civil War Years  
Stewart held many jobs after the Civil War. For a time he worked as a surveyor and at the cotton brokerage business with his brother in New Orleans.  He declined the offer of the presidency of Cumberland University but he returned to the University as a teacher in 1867. He left the university in 1869 due to a throat disease which left him unable to teach.  He moved to St Louis and was employed by the St. Louis Mutual Insurance Company.  In 1874, at a considerable reduction in salary, he accepted the position of Chancellor of the University of Mississippi and moves to Oxford, Mississippi. He resigned in 1886 and in 1888 at the age of 67, he moved back to St. Louis to be with his children and their families. 

In 1890, the Congress provided money for the first National Military Park at Chickamauga and Chattanooga and Stewart was appointed to one of the Civilian Commissioners of the project. The new Park was dedicated over a two day ceremony on September 19 and 20, 1895 on the 32nd anniversary of the Battles.  Stewart was unable to attend the opening ceremony because of an illness which had been misdiagnosed as a heart problem. His son who was a St Louis physician, correctly diagnosed and treated him for Malaria.  Stewart regained his health and resigned his commission in 1900.  Stewart died in 1908 in Biloxi, Mississippi. and he was buried in Bellfontaine Cemetary in St. Louis.