Soldier, surveyor, member of Continental Congress.
Studied in Ireland and became a civil engineer before immigrating to America in the mid-1740s. Settled in Carlisle, Cumberland County, Pennsylvania.
Agent and surveyor of the Penn family. Elected to the Pennsylvania Assembly (1751). Colonel and commander of the provincial militia during the French and Indian War. Presented with a medal by the city of Philadelphia for having destroyed the Kittanning Indian towns (1756).
Magistrate, judge of the Court of Common Pleas (c. 1757), and justice of the peace (1764) for Cumberland County.
Presbyterian elder in Carlisle. A founding trustee of Dickinson College (1773). The first brigadier general commissioned by Congress (1776), he served until April, 1777. Major general of the Pennsylvania State Militia. Delegate to Continental Congress (1779-80).
Born in Brookbor, County Fermanagh, Ireland. Married Rebecca Lyons. Father of John Armstrong, Jr. and James Armstrong. Cousin of Joseph Armstrong (vi, 63n).