Peter Fidler stood outside Chesterfield House and watched a Blackfoot chief named Ac ko mok ki use a stick to draw something on the ground. His sketch on this natural drawing board was, it is believed, the first detailed map of western North America seen by Europeans. Chesterfield House was a trading post built in 1800 by the Hudson’s Bay Company. It stood just east of what is now Alberta, Canada. Peter Fidler was the post’s surveyor. Part of a surveyor’s job was to be a cartographer, or mapmaker. He gathered information about unexplored lands from Indians who came to the post to trade. The Hudson’s Bay Company had been established by King Charles II of England in 1670, and it had done much to promote trade and exploration in the New World. However, at the beginning of the nineteenth century, the plains and mountains to the north, south, and west of Chesterfield House remained a vast, uncharted area. The trading post thus stood at what has been described as “the edge of European knowledge.” This lack of knowledge was soon remedied. Explorations like the Lewis and Clark expedition (1804–1806) provided information about the geography of the continent. As they set out on their history-making venture, Lewis and Clark relied heavily on Ac ko mok ki’s cartography. Fidler had reproduced the chief’s map on paper and annotated it, using details provided by Ac ko mok ki. Little is known about Ac ko mok ki other than the apparent fact that his travels and communication with other American Indians had developed in his mind a remarkable grasp of thousands of square miles of North America. The map he drew for Fidler began at the junction of the Red Deer and Saskatchewan rivers, where the post sat. It provided the first detailed depiction of the wide drainage network of the Missouri River, showing the streams that began in the mountains and fed the river. It helped determine the length and width of the Rocky Mountains, which appeared on the map as parallel lines, and provided information about the land west of those mountains down to the Pacific coastline. Ac ko mok ki’s map was extremely complex. In addition to physical features like rivers and mountains, it indicated where dozens of Indian tribes were located, which parts of the land were forests and which were plains, and how long it took to travel from one place to another. The willingness of the Indians of North America to share their knowledge was a great benefit to the early settlers. What Fidler learned from Ac ko mok ki outside Chesterfield House that day would help the Europeans “discover,” claim, and settle the western half of the continent. What message is the author presenting in this text?