|United States Attorney for the Southern District of New York|
July 1854 – January 1858
|Preceded by||Charles O'Conor|
|Succeeded by||Theodore Sedgwick|
|District Attorney of New York County|
January 1, 1882 – November 22, 1883
|Preceded by||Daniel G. Rollins|
|Succeeded by||John Vincent (Acting)|
February 6, 1846 – December 31, 1850
|Preceded by||Matthew C. Paterson|
|Succeeded by||N. Bowditch Blunt|
|Member of the U.S. House of Representatives|
from New York's 3rd district
March 4, 1841 – March 3, 1843
|Preceded by||Ogden Hoffman|
|Succeeded by||Jonas P. Phoenix|
March 4, 1835 – March 3, 1837
|Preceded by||Charles G. Ferris|
|Succeeded by||Ogden Hoffman|
|Member of the|
New York State Assembly
from New York County
|Born||March 29, 1808|
Albany, New York, U.S.
|Died||November 22, 1883 (aged 75)|
New York City, New York, U.S.
|Alma mater||Columbia College|
John McKeon (March 29, 1808, Albany, New York – November 22, 1883, New York City) was an American lawyer and politician from New York.
He was the son of Capt. James McKeon who fought in the War of 1812. He graduated from the law department of Columbia College in 1828, was admitted to the bar, and commenced practice in New York City.
McKeon was a representative in the New York State Assembly from 1832 to 1834. He was elected as a Jacksonian to the 24th United States Congress, serving from March 4, 1835, to March 3, 1837, but was defeated for re-election. He was elected as a Democrat to the 27th United States Congress, serving from March 4, 1841, to March 3, 1843, but was again defeated for re-election.
In February 1846, he was appointed New York County District Attorney and, when the office became elective under the State Constitution of 1846, was elected in May 1847 to succeed himself. He remained in office until the end of 1850 when his term expired. In this office, he secured the conviction of Madame Restell.
He was appointed by President Franklin Pierce United States Attorney for the Southern District of New York, and served from July 10, 1854, to January 7, 1858. While holding this office, he prosecuted a number of important cases. Among them were the attempt to enlist men to serve in the British Army during the Crimean War, and the seizure of the filibustering ship "Northern Light."
He was again New York County D.A. from 1882 until his death in office. He died at his residence at 44, West 37th Street, and was buried in a family vault under the old St. Patrick's Cathedral on Mott Street in New York City.