During the Mexican-American War, he served as second in command to Winfield Scott and fought at the Siege of Veracruz and the Battle of Cerro Gordo.

He served only three months due to his failure to attack Confederate general Joseph E. Johnston's troops after the Battle of Hoke's Run.

This allowed Johnston to support P. G. T. Beauregard and give the Union Army their first defeat at the First Battle of Bull Run.

He was widely blamed for the Union loss at Bull Run and defended his Civil War performance with his book, A Narrative of the Campaign in the Valley of the Shenandoah, in 1861, published in 1865.

He was a wealthy businessman and owned 30 cotton mills in Pennsylvania, a sugar plantation in Louisiana and other investments in railroads and steamships.

He received his education in public schools[3] and in 1807, worked in a counting room of a business involved in trade with East India.

[1] He volunteered for service during the War of 1812 and rose to the rank of colonel in the Pennsylvania Militia and captain in the United States Army.

[8] Patterson helped quell the Philadelphia nativist riots against Irish Catholics, which resulted in the destruction of St. Michael's and St. Augustine's Churches.

He arrived before Scott at the Siege of Veracruz and overruled a proposed frontal attack of the fortifications by general David E.

[15] His son Francis Engle Patterson and his son-in-law John Joseph Abercrombie also served as Union Army generals during the Civil War.

[18] While underway, he received additional communication from Scott that Johnston was prepared to make "a desperate stand" at Harper's Ferry.

[19] On July 2, Patterson encountered Confederate Brigadier general Thomas J. Jackson at the Battle of Hoke's Run and forced his troops into retreat.

[21] Johnston declared that Patterson's army had largely deterred him from pursuing the shattered and disorganized Union troops as they retreated back to Washington, D.C. following the battle.

[31] At his funeral, his pallbearers included Ulysses S. Grant, William Tecumseh Sherman, Fitz John Porter and Winfield Scott Hancock.