Thousand Islands National Park, on the Saint Lawrence River in Ontario, was established in 1904 as the first Canadian national park east of the Rocky Mountains. Though small, it spans 21 islands, smaller islets, and mainland sites, with much of it accessible only by boat. Its islands are the worn tops of ancient mountains in the Frontenac Axis, within the biodiverse Frontenac Arch Biosphere Reserve. Human use reaches back about 10,000 years, from early hunting and fishing peoples to Iroquois summer encampments, later followed by French travelers and post-Revolution settlement. The area also saw War of 1812 traffic and remains a protected corridor of recreation, ecology, and history.