The Cascade Mountain Range also impedes transportation. Washington operates and maintains roads over seven major mountain passes and eight minor passes. During winter months some of these passes are plowed, sanded, and kept safe with avalanche control. Not all stay open through the winter. The North Cascades Highway, State Route 20, closes every year due to snowfall and avalanches in the area of Washington Pass. The Cayuse and Chinook passes east of Mount Rainier also close in winter.