Yellowstone has five entrances, each with different seasonal access. The North Entrance at Gardiner, Montana is the only one open to vehicles year-round.
By air, the nearest airports are in Bozeman and Billings, Montana; Jackson and Cody, Wyoming; and Idaho Falls, Idaho. West Yellowstone, Montana has a small airport with summer-only service (June to early September). Bozeman is the most popular choice, about 90 minutes from the North Entrance.
By car, the West Entrance (via West Yellowstone) and North Entrance (via Gardiner) are the most commonly used. The Northeast Entrance via Cooke City offers the most scenic approach — the Beartooth Pass from Red Lodge is spectacular, as is the Chief Joseph Scenic Byway from north of Cody. Most entrances open from mid-April to early November; exact dates depend on snow conditions.
Bus service runs from Bozeman to West Yellowstone year-round via Highway 191. There is no public transportation within the park.