• Major General of the U.S. Army Abner Doubleday, 1819
  

In San Francisco, after the war, he obtained a patent on the cable car railway that still runs there. In his final years in New Jersey, he was a prominent member and later president of the Theosophical Society.

Doubleday is often mistakenly credited with inventing baseball, although he never made such a claim, and there is no evidence to support it.

Doubleday was born in Ballston Spa, New York, in a small house on the corner of Washington and Fenwick Streets. The family all slept in the attic loft of the one room house. His paternal grandfather, also named Abner, had fought in the American Revolutionary War. His maternal grandfather joined the Army at 14 and was a mounted messenger for George Washington. His father, Ulysses F. Doubleday, fought in the War of 1812, published newspapers and books, and represented Auburn, New York, for four years in the United States Congress. Abner spent his childhood in Auburn and later was sent to Cooperstown to live with his uncle and attend a private preparatory high school. He practiced as a surveyor and civil engineer for two years before entering the United States Military Academy in 1838. He graduated in 1842, 24th in a class of 56 cadets, and was commissioned a brevet second lieutenant in the 3rd U.S. Artillery.

One of the persistent myths of baseball history is that Doubleday invented the game in 1839, although he was in West Point at the time. To his credit, Doubleday never claimed to have invented baseball. Neither his letters nor his diaries nor his New York Times obituary ever mentions the game, and he was never inducted into the Baseball Hall of Fame. The Doubleday myth appears to have rested solely on the testimony of one elderly admirer who was later committed to an insane asylum.

Doubleday fired the first shots from the Union in the defense of Fort Sumter in a "contest ..., as [to] whether virtue or vice should rule" in America.

Doubleday initially served in coastal garrisons and then in the Mexican - American War from 1846 to 1848 and the Seminole Wars from 1856 to 1858. In 1852, he married Mary Hewitt of Baltimore. In 1858 he was transferred to Fort Moultrie in Charleston harbor, but by the start of the Civil War, he was a captain and second in command in the garrison at Fort Sumter, under Major Robert Anderson. He aimed the cannon that fired the first return shot in answer to the Confederate bombardment on April 12, 1861. He subsequently referred to himself as the "hero of Sumter" for this role.

Doubleday was promoted to major on May 14, 1861, and commanded the Artillery Department in the Shenandoah Valley from June to August, and then the artillery for Major General Nathaniel Banks's division of the Army of the Potomac. He was appointed brigadier general of volunteers on February 3, 1862, and was assigned to duty in northern Virginia while the Army of the Potomac conducted the Peninsula Campaign. His first combat assignment was to lead the 2nd Brigade, 1st Division, III Corps of the Army of Virginia during the Northern Virginia Campaign. In the actions at Brawner's farm, just before the Second Battle of Bull Run, he took the initiative to send two of his regiments to reinforce Brigadier General John Gibbon's brigade against a larger Confederate force, fighting it to a standstill. (Personal initiative was required since his division commander, Brigadier General Rufus King, was incapacitated by an epileptic seizure at the time. He was replaced by Brigadier General John P. Hatch.) His men were routed when they encountered Major General James Longstreet's corps, but by the following day, August 30, he took command of the division when Hatch was wounded, and he led his men to cover the retreat of the Union Army.

Doubleday again led the division, now assigned to the I Corps of the Army of the Potomac, after South Mountain, where Hatch was wounded again. At Antietam, he led his men into the deadly fighting in the Cornfield and the West Woods, and one colonel described him as a "gallant officer ... remarkably cool and at the very front of battle." He was wounded when an artillery shell exploded near his horse, throwing him to the ground in a violent fall. He received a brevet promotion to lieutenant colonel in the regular army for his actions at Antietam and was promoted in March 1863 to major general of volunteers, to rank from November 29, 1862. At Fredericksburg in December 1862, his division mostly sat idle. During the winter, the I Corps was reorganized and Doubleday assumed command of the 3rd Division. At Chancellorsville in May 1863, the division was kept in reserve.

At the start of the Battle of Gettysburg, July 1, 1863, Doubleday's division was the second infantry division on the field to reinforce the cavalry division of Brigadier General John Buford. When his corps commander, Major General John F. Reynolds, was killed very early in the fighting, Doubleday found himself in command of the corps. His men fought well in the morning, putting up a stout resistance, but as overwhelming Confederate forces massed against them, their line eventually broke and they retreated back through the town of Gettysburg to the relative safety of Cemetery Hill south of town. It was Doubleday's finest performance during the war, five hours leading 9,500 men against ten Confederate brigades that numbered more than 16,000. Seven of those brigades incurred casualties that ranged from 35 to 50 percent, indicating the ferocity of the Union defense. But on Cemetery Hill, the I Corps could muster only a third of its men as effective for duty and the corps was essentially destroyed as a combat force for the rest of the battle; it would be decommissioned in March 1864, its surviving units combined into other corps.

On July 2, 1863, Army of the Potomac commander Major General George G. Meade replaced Doubleday with Major General John Newton, a more junior officer from another corps. The ostensible reason was a report by XI Corps commander Majpr General Oliver O. Howard that Doubleday's corps broke first, causing the entire Union line to collapse, but Meade also had a long history of disdain for Doubleday's combat effectiveness, dating back to South Mountain. Doubleday was humiliated by this snub and held a lasting grudge against Meade, but he returned to division command and fought well for the remainder of the battle. He was wounded in the neck on the second day of Gettysburg and received a brevet promotion to colonel in the regular army for his service. He formally requested reinstatement as I Corps commander, but Meade refused, and Doubleday left Gettysburg on July 7 for Washington.

Doubleday's indecision as a commander in the war resulted in his uncomplimentary nickname "Forty - Eight Hours."

Doubleday assumed administrative duties in the defenses of Washington, D.C., where he was in charge of courts martial, which gave him legal experience that he used after the war. His only return to combat was directing a portion of the defenses against the attack by Confederate Lieutenant General Jubal A. Early in the Valley Campaigns of 1864. Also while in Washington, Doubleday testified against George Meade at the United States Congress Joint Committee on the Conduct of the War, criticizing him harshly over his conduct of the Battle of Gettysburg. While in Washington, Doubleday remained a loyal Republican and staunch supporter of President Abraham Lincoln. Doubleday rode with Lincoln on the train to Gettysburg for the Gettysburg Address and Mr. and Mrs. Doubleday attended events with Mr. and Mrs. Lincoln in Washington.

After the Civil War, Doubleday mustered out of the volunteer service on August 24, 1865, reverted to the rank of lieutenant colonel, and became the colonel of the 35th U.S. Infantry in September 1867. He was stationed in San Francisco from 1869 through 1871 and he took out a patent for the cable car railway that still runs there, receiving a charter for its operation, but signing away his rights when he was reassigned. In 1871 he commanded the 24th U.S. Infantry, an all African - American regiment with headquarters at Fort McKavett Texas. He retired in 1873.

In the 1870s, he was listed in the New York business directory as lawyer.

Doubleday spent much of his time writing. He published two important works on the Civil War: Reminiscences of Forts Sumter and Moultrie (1876), and Chancellorsville and Gettysburg (1882), the latter being a volume of the series Campaigns of the Civil War.

In the summer of 1878 Doubleday lived in Mendham, New Jersey, and became a prominent member of the Theosophical Society. When two of the founders of that society, Helena Blavatsky and Henry Steel Olcott, moved to India at the end of that year, he was constituted as the President of the American body. Another prominent member was Thomas A. Edison.

Doubleday died of heart disease in Mendham, and is buried in Arlington National Cemetery in Arlington, Virginia.

Although Doubleday achieved minor fame as a competent combat general with experience in many important Civil War battles, he is more widely remembered as the supposed inventor of the game of baseball, in Elihu Phinney's cow pasture in Cooperstown, New York, in 1839.

The Mills Commission, chaired by Abraham G. Mills, the fourth president of the National League, was appointed in 1905 to determine the origin of baseball. The committee's final report, on December 30, 1907, stated, in part, that "the first scheme for playing baseball, according to the best evidence obtainable to date, was devised by Abner Doubleday at Cooperstown, New York, in 1839." It concluded by saying, "in the years to come, in the view of the hundreds of thousands of people who are devoted to baseball, and the millions who will be, Abner Doubleday's fame will rest evenly, if not quite as much, upon the fact that he was its inventor ... as upon his brilliant and distinguished career as an officer in the Federal Army."

However, there is considerable evidence to dispute this claim. Baseball historian George B. Kirsch has described the results of the Mills commission as a "myth". He wrote, "Robert Henderson, Harold Seymour and other scholars have since debunked the Doubleday - Cooperstown myth, which nonetheless remains powerful in the American imagination because of the efforts of Major League Baseball and the Hall of Fame in Cooperstown." At his death, Doubleday left many letters and papers, none of which describe baseball, or give any suggestion that he considered himself a prominent person in the evolution of the game. Chairman Mills himself, who had been a Civil War colleague of Doubleday and a member of the honor guard for Doubleday's body as it lay in state in New York City, never recalled hearing Doubleday describe his role as the inventor. Doubleday was a cadet at West Point in the year of the alleged invention and his family had moved away from Cooperstown the prior year. Furthermore, the primary testimony to the commission that connected baseball to Doubleday was that of Abner Graves, whose credibility is questionable; a few years later, he shot his wife to death and was committed to an institution for the criminally insane for the rest of his life. Part of the confusion could stem from there being another man by the same name in Cooperstown in 1839.

There is a monument to Doubleday at Gettysburg erected by his men, admirers, and the state of New York. There is a 7-foot (2.1 m) obelisk monument at Arlington National Cemetery where he is buried, located about 130 feet (40 m) behind the Lee Mansion. There was a movement to petition the postmaster general to issue a U.S. postage stamp for him in 2011, commemorating the 150th anniversary of Fort Sumter. Doubleday Field is a minor league baseball stadium named for Abner Doubleday, located in Cooperstown, New York, near the Baseball Hall of Fame. It hosted the annual Hall of Fame Game, an exhibition game between two major league teams that was played from 1940 until 2008.

The Auburn Doubledays are a minor league baseball team based in Doubleday's hometown of Auburn, New York.

Doubleday Field at West Point, New York, where the Army Black Knights play at Johnson Stadium, is named in Doubleday's honor.

The Abner Doubleday Little League and Babe Ruth Fields in Ballston Spa, New York, the town of his birth. The house of his birth still stands in the middle of town and there is a monument to him on Front Street.

Doubleday's purported invention of baseball was such a widely accepted belief in the late 19th century, that the legend was recorded on a Civil War monument in Maryland in 1897. The Doubleday Hill Monument, erected in Williamsport, Maryland, to commemorate Doubleday's occupation of a hill there during the Civil War, claims he invented the game in 1835.