The region that became Glacier National Park was first inhabited by Native Americans and upon the arrival of European explorers, was dominated by the Blackfeet in the east and the Flathead in the western regions. Soon after the establishment of the park on May 11, 1910, a number of hotels and chalets were constructed by the Great Northern Railway. These historic hotels and chalets are listed as National Historic Landmarks, and a total of 350 locations are on the National Register of Historic Places. By 1932, work was completed on the Going-to-the-Sun Road, later designated a National Historic Civil Engineering Landmark, which provided greater accessibility for automobiles into the heart of the park.
The mountains of Glacier National Park began forming 170 million years ago when ancient rocks were forced eastward up and over much younger rock strata. Known as the Lewis Overthrust, these sedimentary rocks are considered to have some of the finest fossilized examples of extremely early life found anywhere on Earth. The current shapes of the Lewis and Livingston mountain ranges and positioning and size of the lakes show the telltale evidence of massive glacial action, which carved U-shaped valleys and left behind moraines which impounded water creating lakes. Of the estimated 150 glaciers which existed in the park in the mid-19th century, only 25 active glaciers remained by 2010. Scientists studying the glaciers in the park have estimated that all the glaciers may disappear by 2020 if the current climate patterns persist.
Glacier National Park has almost all its original endemic plant and animal species. Mammals such as the grizzly and mountain goat as well as less common ones such as the wolverine and lynx are known to inhabit the park. Hundreds of species of birds, more than a dozen fish species and even a few reptile and amphibian species have been documented. The park has numerous ecosystems ranging from prairie to tundra and the easternmost forests of red cedar and hemlock normally found in large numbers closer to the Pacific Ocean. Though larger forest fires are uncommon in the park, in 2003 over 10% of the park was impacted by fires.
Glacier National Park borders Waterton Lakes National Park in Canada-the two parks are known as the Waterton-Glacier International Peace Park, and were designated as the world's first International Peace Park in 1932. Both parks were designated by the United Nations as Biosphere Reserves in 1976, and in 1995 as World Heritage sites.