In 1755 Benjamin Franklin, Postmaster General of PA, obtained 150 wagons and 250 pack horses from York and Lancaster and Cumberland Counties to be taken to Pittsburgh for Braddock's expedition at Fort Duquesne near Pittsburgh. Yost at the age of 14 was a teammaster in that expedition and was Captain of the 7th battalion York Co Militia. He served with General Braddock on the expedition against Fort Duquesne and saw service at Bloody Run during Indian War. He died of Asiatic cholera at the home of his son-in-law Benjamin Emmert. The body was buried at Antietam, near Hagerstown but was later removed to the Emmert lot near Funkstown, Maryland. He was a large man - over 6 feet tall. He often wore a blanket in place of an overcoat, and sometimes went on foot by choice.