About the Event

The Whitehorse Oso Strong Half Marathon is a community-centered, recreational 13.1-mile out-and-back run through the serene beauty of the Stillaguamish Valley. Beginning and ending at the Fortson Mill Trailhead, this event invites participants to run or walk through forested landscapes, open valleys, and the meaningful grounds of the Oso Slide Memorial. Open to both runners and walkers, this non-competitive event is designed for all levels. 

Participant Amenities

All registered participants will receive:

• Chip-timed results

• Finisher Medal

• Event T-Shirt for registrations completed by March 15

• Awards for the Top 3 Overall Male and Female Finishers

• Post-race refreshments, including hydration and light snacks at the finish area 

Community Contribution:

A portion of event fees will be donated to the Community Foundation of Snohomish County to support long-term care of the Oso Slide Memorial.

Course Overview — Out-and-Back (13.1 miles) 

The course follows the Whitehorse Regional Trail, a wide, flat, compact-gravel surface ideal for all experience levels. Participants start at Fortson Mill Trailhead, travel west toward the C-Post Road Trailhead, and complete their turnaround with a respectful loop inside the Oso Slide Memorial Park.

Key Course Features

• Flat, compact-gravel trail

• Gentle grades and wide path

• Forest, valley, and mountain views

• Volunteers stationed throughout the route

• Clearly marked “in/out” turnaround loop at the Slid memorial Park

Turnaround & Aid Station (Mile ~6.5) | SR 530 Slide Memorial Park

• Water

• Electrolytes

• Basic first aid

• Portable Restroom

• Course marshals guiding flow

Course Maps

Event Schedule

• Check-In & Packet Pick-Up: 09:00 AM - 10:15 AM

• Start Time: 10:30 AM

• Course Open: 10:30 AM - 2:00 PM 

Restrooms

Portable restrooms will be available for participant convenience at the following locations:

• Start/Finish Area: Fortson Mill Trailhead

• Turnaround Point: Oso Slide Memorial Park Loop

Please plan accordingly and allow extra time before the start. We appreciate your help in keeping these facilities clean and accessible for all participants.

Parking & Access

• Primary Parking - Fortson Mill Trailhead Lot 

Address: 30518 Fortson Mill Road, off of SR 530 near Arlington, WA 

Take exit 208 off of I-5 and drive east on Highway 530 to Arlington. From Arlington, continue east on 530 for 21 miles. When you see the overhead power lines, be prepared to turn left onto Fortson Mill Road. Parking is on the left approximately 100 yards down the road. We will have event signs on the road. 

• Spectator Parking — C-Post Rd Trailhead (Turnaround Area - The Slide Memorial Park)

Address: 29415 SR 530 NE, Arlington, WA 98223 

Take exit 208 off of I-5 and drive east on Highway 530 to Arlington. From Arlington, continue east on 530 for approximately 16.7 miles. Parking will be on your left. This is an excellent place for family and friends to park and walk to the Oso Slide Memorial to cheer on participants at the turnaround point. 

All registration fees are non-refundable. For full details, please review our Refund Policy.