Heading east from Marblemount, Highway 20 enters North Cascades National Park after five miles, then passes Goodell Creek and Newhalem Campgrounds, the turnoff to North Cascades Visitor Center, and Skagit General Store in Newhalem.

The little settlement of Newhalem is a quiet company town with only one focus, producing electricity for Seattle at nearby Gorge, Diablo, and Ross dams. The parklike grounds are surrounded by trim clapboard homes occupied by employees of Seattle City Light.

In the town park find Old Number Six, a 1928 Baldwin steam locomotive that hauled passengers and supplies to the Skagit River dams; today it’s a favorite of kids. The small Seattle City Light Visitor Center here makes a good restroom stop.

East of Newhalem, Highway 20 begins a serious climb into the forested Cascades, and quickly passes a chain of three dams and reservoirs—Gorge, Diablo, and Ross—that constitute the centerpiece of Ross Lake National Recreation Area (a part of North Cascades National Park). Tours of Diablo Dam and Lake are a popular attraction here. Be sure to stop at the Forge Creek Falls overlook near milepost 123 for views of the creek plunging into the gorge below.

Colonial Creek Campground is along the highway near Diablo Lake, and a mile east is an overlook where you can peer down on the emerald green lake waters and across to the jagged summits of Pyramid Peak and Colonial Peak.

Continuing eastward, the highway climbs along Granite Creek before topping two passes—4,855-foot Rainy Pass and 5,447-foot Washington Pass. A short paved trail leads from Washington Pass to over-the-highway viewpoints of 7,720-foot Liberty Bell—the symbol of the North Cascades Highway—and Early Winters Spires. Beyond this, the highway spirals downward to Methow Valley and the town of Winthrop, 30 miles to the east and 3,600 feet lower.