North Cascades Highway: Marblemount to Winthrop
86 miles of State Route 20 from Marblemount to Winthrop, the last major road built across the Cascade Range in Washington (opened 1972) and the highest state highway pass crossing in the state at Washington Pass (5,477 ft). Old-growth forest, waterfalls and alpine scenery on a sustained mountain crossing rather than a short technical burst.
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Closed every winter across the mountain section — typically mid-November through late April or early May, with exact dates set by snowpack each year, not a fixed calendar. This is the single most common way people get caught out here: a mapped road is not the same as a currently open one. Check current access · Reviewed 2026-09-23
Planning the drive
This is a sustained mountain crossing, not a short technical burst: 87 counted bends over 86 miles is a density of 1.0 per mile, wide sweeping curves through old-growth forest rather than tight switchbacks. Our own measured high point came back at 5,457 ft against Washington Pass's documented 5,477 ft — close enough to confirm the trace. The road wasn't completed until 1972, the last major crossing of the Cascade Range in Washington to be built. NPS: North Cascades Highway
This road closes completely every winter, typically mid-November through late April or early May, with the exact dates set by that year's snowpack rather than a fixed calendar — gates go up at both ends and the mountain section is genuinely impassable, not just discouraged. Check current WSDOT mountain pass status before planning a trip near either end of the season.
Roads to connect
- Sherman Pass · SR 20The same SR 20 continues much further east to a second, lower-traffic mountain crossing near Republic.
Driving notes updated .
Road shape
- Length
- 86 mi
- Bends
- 87
- Switchbacks
- 4
- Bends per mile
- 1
- Turning per mile
- 127°
- Curviest rank
- 144of 160
Measured from the OpenStreetMap centreline at a 20 m sampling step — road shape only, not a safety or speed judgement. How bends are counted.
Elevation
- Total climb
- 12,577ft
- Climb per mile
- 146ft
- Highest point
- 5,457ft
- Steepest grade
- 6.9%
Sampled every 100 m from USGS 10 m elevation data, a public-domain federal dataset. Total climb counts vertical change in both directions, so it does not depend on which way you drive. How elevation is measured.
Speed limits
Varies
Unverified
Check posted signs along the road.
No reliable posted limit was found for this selected section. Follow current signs.
Posted signs always govern. How speed evidence is handled.
Sources
Difficulty 2/3 (Winding) is our editorial rating of width, bends and sightlines; “Medium speed” describes character, not a target speed. Full method. Identified from:
- NPS: North Cascades Highway
- Wikipedia: Washington State Route 20
- OpenStreetMap road data (78 ways in this trace)
Reviewed 2026-09-23. The trace shows selected road sections, not a navigation route.
Roads nearby
Distances are approximate straight lines between road centers, not driving distances or direct connections.