Alaska is over 650,000 square miles and much of that has no road access. The primary forms of transportation in areas without roads are by air or sea, so the Alaska Marine Highway is a big part of the 'highway system.' It is such a unique set of routes that is has been designated as a National Scenic Byway and an All American Road, the only marine route with this distinction.
With its southernmost port in Bellingham, WA, the Alaska Marine Highway extends more than 3,500 miles to Dutch Harbor, with over 30 stops along the way. Taking a ferry is an excellent way to see a huge swath of Alaska's coastline while visiting unique communities along the way.