Filming took place at both Pinewood Studios and Elstree Studios in England. The set for the Overlook Hotel was then the largest ever built. It included a full recreation of the exterior of the hotel, as well as all of the interiors. A few exterior shots were done at Timberline Lodge on Mount Hood in Oregon. They are noticeable because the hedge maze is missing. The interiors are based on those of the Ahwahnee hotel in Yosemite National Park. The Timberline Lodge requested Kubrick change the sinister Room 217 of King's novel to 237, so customers would stay in their own room 217 fearlessly.
The opening panorama shots (which were used by Ridley Scott for the closing moments of the film Blade Runner) and all scenes of the Volkswagen Beetle on the road to the hotel were filmed in Glacier National Park in Montana. These scenes were filmed out of a helicopter, which can be seen briefly in the open-matte version of the film in the lower right-hand corner of the screen.
Source: Yahoo Answers.
May or may not be credible, but seems legit.