Sergeant Patrick Gass was born in Pennsylvania, June 12, 1771. In 1789, he joined the armed forces. When Gass had joined the expedition, he was selected to fulfill being Sergeant for Sergeant Charles Floyd who had died August 20, 1804. The first Christmas at Fort Mandan, Gass wrote in his journal, "This evening we finished our fortification. Flour, dried apples, pepper and other articles were distributed in the different messes to enable them to celebrate Christmas in a proper and social manner. On Christmas Day he wrote, "Captain Clark then presented to each man a glass of brandy, and we hoisted the American flag in the garrison, and its first waving in Fort Mandan was celebrated with another glass. The men cleared out one of the rooms and commenced dancing, which was continued in a jovial manner till 8 at night." Patrick Gass died April 2, 1870 at 99 years old. He was the longest living member of the "Core of Discovery."