Arlington, where the river's two forks meet

Arlington sits on a glacial terrace in the foothills of the Cascade Range, and its downtown stands on a bluff above the confluence of the Stillaguamish River and its North and South Forks. Haller Park, two and a half acres of city ground at 1100 West Avenue, sits on the river; the City of Arlington describes it as a popular spot to view eagles or fish along the riverbank. This is the day the walk stops being suburban. North of Marysville the ground opens into river valley and farmland.

The town was established at a railway depot in March 1890 and incorporated as a city in May 1903, and it was known locally as the Shingle Capital of the World — though mills in Everett and Ballard produced more shingles at the time. The railway that established it, the Seattle, Lake Shore and Eastern, is now a trail. Thirty miles of Snohomish County's Centennial Trail run on the right-of-way of that railway's Sumas Branch, built in 1889 by a line that specialized in hauling timber, lumber and metals, and the trail now connects Snohomish, Lake Stevens and Arlington up to the Skagit County line. Development began in 1989 during Washington's centennial, and the final segment, Arlington to the county line, opened in 2013.

Arlington also has a hospital. Cascade Valley Hospital has 48 beds and a Level IV trauma center; it opened as Arlington General Hospital in 1909 and moved to its present campus in 1958. Since 2016 it has been run under a thirty-year lease by Skagit Regional Health, the same system that operates the hospital in Mount Vernon two days further up this road. A community hospital is usually where a blood count that looks wrong gets looked at first. It is not where a marrow or blood stem cell transplant happens. That gap — between the place that finds the problem and the place that can treat it — is a large part of why she is walking, and why she keeps asking people to join a registry before anyone needs them to.