Born at brand-new York City, June 2, 1815, the scion of great wealth and social position, the nephew of General Stephen W. Kearny of Mexican War fame. In his early years he attended private schools, and graduated from Columbia University, 1833, studied law, traveled widely.
In 1836 he inherited one million dollars from his grandfather and at once embraced military career which had been his goal since boyhood. A superb horseman, he was commissioned a 2nd Lieutenant in his uncle’s regiment, the 1st Dragoons, 1837. In 1839 attended the French Cavalry School at Saumur, saw action with Chasseurs d’ Afrique in Algiers in 1840, and after return to the United States acted as Aide-de-Camp successively to Alexander Macomb and Winfield Scott, generals-in-chief of army. In 1846 his company served as escort for Scott during advance on Mexico City, and at Churubusco his left arm was shattered, necessitating amputation. For gallant conduct he was breveted Major.
After later service in California he resigned the from army in 1851 and went around the world. He had also resigned on April 5, 1846, but reinstated 5 weeks later upon outbreak of Mexican War.
Following several years spent on his brand-new Jersey estate, he went abroad again in 1859 and served in Napoleon III’s Imperial Guard during the Italian War. He is said to have taken part in every Cavalry charge at Magenta and Solferino with the reins clenched in his teeth.
When the Civil War broke out, he hurried home and offered his services. He was among the 1st Brigadier Generals of Volunteers appointed (August 7 to rank from May 17, 1861) and was assigned to command a brigade of brand-new Jersey regiments in Franklin’s Division. During the course of the Peninsular campaign in the spring of 1862, he rose to command of the Division of Cavalry in Samuel P. Heintzelman’s III Corps and was made a Major General as of July 4, 1862. At close of 2nd Manassas campaign, during the indecisive engagement of Chantilly (Ox Hill) September 1, 1862, he inadvertently rode into the Confederate lines and was killed instantly by a rifle ball as he wheeled and spurred off.
He was the originator of the "Kearny Patch," the forerunner of the corps badges later developed by General Daniel Butterfield, and was termed by General Scott "the bravest man I ever knew, and a perfect soldier." His remains, forwarded under a flag of truce by Robert E. Lee, were 1st buried in Trinity Churchyard in brand-new York City, but on April 12, 1912 were moved to Arlington National Cemetery. His grave is marked by one of only two equestrian statues in the cemetery and was a gift of the people of brand-new Jersey in 1914. The statue was designed-built by Edward Clark Potter