The Canadian government declared Kootenay a national park in 1920, when British Columbia agreed to relinquish the land 5 miles (8 km) on either side of the Trans-Canada Highway in exchange for federal funds to complete the highway's construction. In 1930 the park's area was some 590 square miles (1,520 square km), but it has since been reduced to 543 square miles (1,406 square km).

Since prehistoric times, Kootenay has functioned as a major north-south travel route. Pictographs indicate that humans settled near the hot springs (hot spring) about 11,000 to 12,000 years ago. The park is drained by the Kootenay, Vermilion, and Simpson rivers, and its scenery is characterized by snowcapped peaks (including the Verendrye, Stanley, and Deltaform mountains), glaciers, cascades, canyons, and verdant valleys. Trees of the region include the fir, spruce, and, to a lesser extent, aspen. The park is home to wapiti (elk), moose, deer, bighorn sheep, mountain goats, and beavers.