OverviewSilo Mountain is a mid-elevation peak located in Skagit County, Washington. Also known by some locals as "Big Haystack", Silo Mountain is most notable for being the 90th-most prominent peak in Washington. Silo Mountain has 2430' of prominence, despite only having 4150' total elevation.
Ascents of Silo Mountain are considered non-technical and can be done year-round. However, there are advantages to different route conditions. Most of the summit approach is via Gilligan Creek Road, a logging road located northwest of the peak. The road has active logging and quarry activities, and is generally easiest to travel during weekends. There are even some great views to the north and west during the first-half of the summit approach, helping make the route more aesthetically enjoyable.
The peak, itself, is considered by many people to be easier to summit while the upper slopes are still snow-covered, to limit bushwhacking. It could be suggested that Spring months or late Autumn/early Winter ascents might be most suitable, while the road is at least mostly snow-free but while the upper slopes of Silo Mountain are snow-covered. Many summiters choose to hike, snowshoe, bike, and/or any combination of those modes of transportation.
Getting ThereSTARTING AT MOUNT VERNON, WA:
1) From I-5 and College Way (Exit 227), head east along College Way (a.k.a. Highway 538).
2) After 3.6 miles, at a roundabout, turn left and head north on Highway 9.
3) After 4.3 miles further, turn left onto South Skagit Highway.
4) After 6.0 miles along South Skagit Highway, just after passing Old Day Creek Road and then Gilligan Creek immediately afterwards, turn right onto East Gilligan Creek Road.
5) Immediately veer right.
6) The road then immediately splits again. Veer left, heading uphill.
7) Park off the side of the road before reaching the entrance gate for the logging road, also known as Gilligan Creek Road.
SUMMIT APPROACH FROM GATE:
1) Hike, bike, or snowshoe south along Gilligan Creek Road, which is a gravel logging road that remains on the east side of nearby Gilligan Creek.
2) After ~5.5 miles, at approximately 2900' elevation, turn left (north-northeast).
3) After ~1.5 miles further, at approximately 3750' elevation, turn right (southeast).
NOTE: Heading straight at this road intersection would soon lead directly to Haystack Mountain.
4) After ~0.5 miles further, at approximately 4000' elevation, turn left (east) around the northwest side of a hill located west of Silo Mountain.
5) After ~0.25 miles further, at approximately 3950' elevation, leave the road and head south up the forested upper slopes of Silo Mountain to its summit.
NOTE: The northwest slopes might be the least technical (easiest) to ascend, depending on conditions.
SUMMIT APPROACH: ~Eight miles from gate to summit, with 4000' of elevation gain.
A short side-trip (~0.5 miles roundtrip from the Silo Mountain route) could be done for the summit of nearby Haystack Mountain.
Red TapeThe roads leading to/from Silo Mountain have active logging and quarry activities. Try to plan summit attempts on weekends or holidays, while such official activities are potentially at a minimum.
Logging and quarry operations, machinery, and vehicles have the right-of-way.
Do not park directly in front of the entrance gate. If the gate is open, it is still highly recommended to not enter beyond the gate with a vehicle, as the gate can be shut and locked unexpectedly at any time at the vehicle owner's expense.