Devils Tower National Monument

Where it sits. Devils Tower stands above the Belle Fourche River in Crook County, north-eastern Wyoming, on the western fringe of the Black Hills between the small towns of Hulett and Sundance. The summit reaches 1,558 m above sea level, roughly 386 m above the river and about 265 m above the boulder field at its own base. It is visible from more than 40 km away across rolling ponderosa and grassland, and the approach along State Route 24 delivers it in stages: a grey smudge, then a tooth, then a fluted column that fills the windscreen. Theodore Roosevelt proclaimed it the first national monument of the United States on 24 September 1906, under the newly passed Antiquities Act.

What built it. The rock is phonolite porphyry, an igneous intrusion that pushed into sedimentary layers around 50 million years ago and cooled slowly underground. As it cooled it contracted and fractured into the columns that give the tower its fluting - mostly hexagonal in cross-section, some four- or five-sided, and among the largest columnar joints anywhere in the world, up to 3 m across and over 180 m long. The surrounding softer sedimentary rock has since eroded away, leaving the intrusion standing. Whether it was a volcanic neck, a laccolith or a stock is still debated by geologists; the field evidence has not settled it. The boulder field at the base is the accumulated debris of columns that have peeled away, and no column is known to have fallen in recorded history.

A sacred place first. More than twenty Northern Plains tribes hold this rock sacred, and their names for it long predate the 1875 mistranslation that produced "Devils Tower". The Lakota call it Matho Thipila, Bear Lodge; Kiowa and Cheyenne accounts describe girls or boys fleeing a bear, lifted up on rising rock while the bear's claws scored the sides - the fluting. Prayer cloths and tobacco bundles tied to trees near the trail are active offerings, not decoration, and should be left untouched and unphotographed. Since 1995 the National Park Service has asked climbers to observe a voluntary closure through the whole of June, when Sun Dances and other ceremonies take place; most climbers comply, and climbing numbers that month fall sharply.

On screen. Steven Spielberg made this rock the destination of Close Encounters of the Third Kind (1977) - the shape Richard Dreyfuss's character sculpts obsessively out of mashed potato and modelling clay before recognising it on television. Location filming ran in the autumn of 1976. A detail location hunters enjoy: the Park Service declined to allow the production to shoot inside the monument, so the crew worked from the adjoining Driskill family ranch, which is why so many of the film's angles look at the tower across open pasture rather than from the visitor centre. The climactic mothership landing was not shot in Wyoming at all - it was staged inside a disused wartime dirigible hangar at Brookley Field in Mobile, Alabama, a space several times the size of a normal sound stage. The film brought a wave of visitors that has never entirely receded.

What you actually see today. The Tower Trail is a paved 2.1 km loop that circles the base through the boulder field, close enough to see chalk on the cracks and hear climbers talking; it has gradients that make it demanding for wheelchair users but is otherwise the easiest way to grasp the scale. The Joyner Ridge and Red Beds trails run longer and quieter loops with the best distant compositions. A prairie dog town beside the entrance road is a genuine attraction in its own right. Around 5,000 climbers a year attempt the roughly 220 crack routes; the first recorded ascent was in 1893, when local ranchers William Rogers and Willard Ripley climbed a wooden stake ladder they had driven into a crack, remnants of which are still visible.

Getting there and timing. The monument is 45 km north of Interstate 90 at Sundance, about 175 km from Rapid City, South Dakota. Peak season runs May to September; the Sturgis motorcycle rally in early August fills every room within 150 km. Spring and autumn are quiet and cold, winter closes the campground but leaves the road open. Late afternoon light on the west face is the photographers' choice, and the tower's dark silhouette against a star field has made this a well-known night-sky site. A small entrance fee is charged per vehicle, the America the Beautiful pass is valid, and the campground beside the Belle Fourche River at the base opens from spring to autumn.