[3][4] From Oso continuing towards Darrington, the Whitehorse Trail passes through the historic towns of Fortson and Hazel, and the modern community of Swede Heaven, which hosts a trailhead.

[10] In November 1990, major floods in the Stillaguamish River basin left the railroad damaged and unusable, leading to its formal abandonment by Burlington Northern.

[11] In November 1993, the Snohomish County Council approved $550,000 paid to Burlington Northern to acquire 515 acres (208 ha) on the corridor, with the intent of converting into a recreational trail.

In the aftermath of the mudslide, which killed 43 people, the Whitehorse Trail became a key project in the recovery of the area, employing local workers and drawing tourists.

[15] A 9.5-mile-long (15.3 km) segment of the Whitehorse Trail from Oso to Cicero Pond was expected to be completed in 2018, using $4.24 million in funds from the county government, Washington State Department of Transportation and Federal Emergency Management Agency (FEMA).