Not every entrance is open year-round. In general, Yellowstone National Park closes for the winter: Interior roads close to wheeled vehicles on the Monday after the first Sunday of November, and reopen to over-the-snow vehicles mid-December through mid-March.
Here is a listing of the five main entrances.
The West Entrance is accessed via West Yellowstone on U.S. Highways 191 and 287. It opens to wheeled vehicles from the third Friday in April through the first Sunday in November, and to tracked snowmobiles from the third Monday in December to the Monday of the second full week in March.
(Jackson Hole and Moran, Wyoming)
The South Entrance is accessed via Jackson Hole and Moran on U.S. Highways 191/89/287. This entrance opens on the second Friday of May and stays open through the first Sunday in November. The entrance is closed until the third Monday in December, when it opens to snowmobiles, until the Monday of the second full week in March.
The East Entrance is accessed via Cody on U.S. Highways 14, 16, and 20. This entrance is opened to wheeled vehicles from the second Friday of May through the first Sunday in November, and to tracked snowmobiles from the third Monday in December to Monday of the second full week in March.
The North Entrance is accessed via U.S. Hwy. 89, which runs from Livingston south through the Paradise Valley to Gardiner, Montana. This entrance to provides outside access to the park year-round, allowing cars and trucks access to Mammoth and the Upper Mammoth Terrace, to Tower Junction, and to the Northeast Entrance. In winter (November through April), the North entrance provides the only access to Cooke City, Montana.
(Cooke City and Silver Gate, Montana, via U.S. Hwy. 212 and the Beartooth Highway)
The Northeast Entrance is located outside of Silver Gate, Montana, though many identify it with nearby Cooke City. The Northeast Entrance is open year round with the following restrictions: you can only enter from the east or travel west of this entrance from late spring to early October, and from mid-October to late May the road is plowed only to Cooke City to serve the town’s year-round residents.
From mid-October to late May you cannot travel east of Cooke City as U.S. Hwy. 212 is closed to wheeled because of snow conditions.
The Northeast Entrance is a popular one for those arriving via the Beartooth Highway (discussed in more depth in this section).