This is a ride I've been wanting to do for a couple years, and Saturday's gorgeous weather made it finally happen.
I drove my bike to Darrington, wondering where to park. I've been through there enough (always on my way to or from the North Cascades) to know you can't just park on the street, at least not on the main road, and this is one of the reasons I haven't done the ride yet. Turns out the gas station will let you leave your car behind for several hours while you ride, if you fill your tank there.
The ride is moderate in length (20 miles each way) and pretty flat. Mostly the road is forested on both sides, with incredible peek a boo views of the mountains in every direction. There are no stores, water fountains, or anything like that between the start and end points, but there's a store in Darrington and another at the North Cascades highway. Better to bring your own provisions, though. There are a few creeks you'll pass along the way for water if you bring a purifier, and access to a boat launch on the Sauk.
If you've never been to Darrington, it'll drop your jaw. Spring is the best time to do this ride, the mountains are breathtaking while they're still covered in snow.
Side note: last year I did a ride that was going to be from Arlington to Darrington, but turned back at the construction that's been going on for years. Looks like that's finally complete!