During the expedition, Walker gave names to many topographical features, including the Cumberland Gap. His party built the first non-Indian house (a cabin) in Kentucky, and helped Virginia pioneer Samuel Stalnaker build his home on the westernmost point in colonial Virginia. Walker kept a daily journal of the trip. During some of his expeditions, Walker explored with fellow Virginian, Indian agent, legislator, surveyor and later Revolutionary war general, Joseph Martin, as some of the first colonialists to travel in this area. Martin's son, Revolutionary War officer Col. William Martin, described the naming of the area and river in a letter to historian Lyman Draper, A treaty with the Cherokees was held at Fort Chiswell on New River, then a frontier. On the return of the chiefs home, Dr. [Thomas] Walker, a gentleman of distinction, and my father, [General] Joseph Martin, accompanied them. The Indians being guides, they passed through the place now called Cumberland Gap, where they discovered a fine spring. They still had a little rum remaining, and they drank to the health of the Duke of Cumberland. This gave rise to the name of Cumberland Mountain and Cumberland River. At the age of 64, Walker again traveled to the western areas of Kentucky and Tennessee; he had been commissioned to survey the border between westward of the Virginia and North Carolina. (At that time each state claimed the land to the west of their boundaries for ultimate settlement by the right of discovery.) Because the border was mapped and surveyed, rather than created along the natural boundary of a river, it was considered controversial. It was called the "Walker Line", and still constitutes the border between Kentucky and Tennessee from east to west terminating at the Tennessee River. Walker was influential in dealing with Indian affairs. He was appointed to represent Virginia at the Treaty of Fort Stanwix and Treaty of Lochaber (1770), and dealt with the peace negotiations after the Battle of Point Pleasant. In 1775, Walker served as a Virginia commissioner in negotiations with representatives of the Iroquois Six Nations in Pittsburgh, as the colonies tried to engage them as allies against the British. He is credited as the first to discover and use coal in Kentucky. Due to his broad knowledge of the areas and their resources, Walker became an adviser to Thomas Jefferson from 1780 to 1783 as the future President wrote his Notes