After the war he served in the Continental Congress, and later played an active role in ending the Whiskey Rebellion in Pennsylvania.

[1] Irvine had two brothers, Andrew who was an officer in the Continental Army, and Matthew, who was a physician and a surgeon in General Charles Lee's division.

Irvine's youngest son, Armstrong,[c] also served in the War of 1812, as Adjutant General of the Militia of the Commonwealth of Pennsylvania.

On June 16 of that year he was captured, along with a large number of his fellow officers and men, in Canada at the Battle of Three Rivers during the Lake Champlain campaign and was not exchanged until May 6, 1778.

[6][9] On September 25, 1781, Irvine received orders from Congress to command the Western Department of the Continental Army, which was headquartered at Fort Pitt.

Irvine sent Washington a detailed plan for an offensive in February 1782, that with an estimated 2,000 men, five artillery pieces and a supply caravan, he could move on Detroit and capture it.

In a letter, dated December 2, 1781, to General Washington Irvine reported, "I never saw troops cut so truly a deplorable, and at the same time despicable, a figure.

[15] Irvine became a member of the Continental Congress in 1786 and was selected with John Kean and Nicholas Gilman for settling the accounts of the U.S. Government with the several states.

[6] Irvine unsuccessfully ran for the U.S. Senate in 1788[16] and the 7th congressional district in 1791[17], and was later elected as a U.S. representative from Pennsylvania in the 3rd Congress, serving from December 2, 1793, to March 3, 1795.

[6][18] Irvine continued his involvement in Pennsylvania's public life, overseeing and directing the distribution of lands that were donated to war veterans.

In the 1790s, Irvine played a significant role in surveying lands and laying out the boundaries of towns in western Pennsylvania.

[19] Irvine purchased several tracts of land near the mouth of Brokenstraw Creek at the Allegheny River, some of which he gave to his son Callender.

During 1797, rising tensions between France and the United States led the American government to seek financing with which to improve the military and prepare for what became the Quasi-War.

When it was closed in the 1950s, the graves of a few Revolutionary War officers such as Irvine were identified by the rector of Old Swedes' and reburied at Gloria Dei Church cemetery.

[29] Irvine's correspondence from the early 1790s also includes discussions about the staff and curriculum at Dickinson College in Carlisle, Pennsylvania, the improvement of inland navigation in Pennsylvania, the aftermath of the French Revolution, and Irvine's business ventures with his business partners Charles and John Wilkins, Junior, of Pittsburgh.