From June to December 1809, he served briefly as President pro tempore of the United States Senate.

During part of his service in the Senate, he served as President pro tempore.

Prior to his election to the United States Congress, he had served in the militia during the American Revolution, and had been a tutor at the College of Philadelphia, from 1779 to 1783.

Two of his grandsons, Andrew Gregg Curtin and James Xavier McLanahan, were prominent Pennsylvania politicians.

[1] Gregg died May 20, 1835, in Bellefonte, Pennsylvania, in Centre County, at the age of 79, and was buried in Union Cemetery.