Isaac first appeared in Sussex Co., NJ records on Mar. 13, 1752 when he and George witnessed the will of Samuel Hunt Sr. of Hardwick Twp. About 1769, it is speculated that Isaac went with his brother George to Loudoun Co., VA. In 1771, he appears on a list of tithables in Loudoun Co. with George. He also appears in a later tax list, dated 1773-79. By 1781 he moved to Pennsylvania, where he is listed on a Washington Co. tax list. An Isaac Pettit is listed in Ensign David Ruble's Co. of Washington Co. militia between 1782-85, however, this is may be Isaac Jr., since Isaac Sr. would be in his fifties. On 15 Nov 1793, Isaac bought land from Christopher Slusher on Ten Mile Creek. (This is probably the same Christopher Slusher who is ancestral to our Mahala Slusher. Christopher moved from Washington Co., Maryland to Montgomery Co., Virginia in 1793. The Ten Mile Creek area of Washington Co. was disputed between Pennsylvania and Maryland.) A 1796 tax list showed Isaac with 193 acres, house and barn, two horses and two cows.

Isaac wrote his will on Jan. 12, 1801, and it was proved Sept. 5, 1807. In it he mentions his sons Nathaniel, Charles, David, Isaac, Azariah and John, and daughters Rebecca Jackson and Abigail Masters. An account of his estate was filed August, 1805 in Washington Co. Orphans Court. Source: Washington Co., PA wills, Book 2.