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Happy Isles Fen Boardwalk
A rare Sierra wetland boardwalk steps from the Mist Trail trailhead
About
The Happy Isles Fen Boardwalk is a short, flat loop at the east end of Yosemite Valley, built to protect one of the Sierra Nevada's few true fens — a peat-forming wetland fed by snowmelt rather than a typical mountain stream. The boardwalk sits right next to the Happy Isles Nature Center, steps from where the Mist Trail and John Muir Trail begin their climb toward Vernal and Nevada Falls.
Why This Spot Is Different
Fens are rare in California's dry-summer climate, and this two-acre wetland is one of the few examples in the Sierra Nevada. Groundwater fed by slow snowmelt off the high country near Glacier Point keeps the soil saturated year-round, letting peat accumulate instead of washing away like it would along a normal creek bed. In 2002, park crews restored the site with native replanting, removed old sand fill, and installed split-rail fencing and boardwalks so foot traffic wouldn't compact the fragile ground.
Walking the Boardwalk
- Distance: About half a mile of easy, flat boardwalk trail
- Difficulty: Easy — minimal elevation change, suitable for most visitors
- Best season: Spring into early summer, when snowmelt keeps water moving visibly across the wetland
- Location: Just west of the Happy Isles Nature Center, at the Mist Trail/John Muir Trail trailhead area
Stay on the boardwalk rather than stepping onto the fen itself — the peat and plant life here took centuries to form and don't recover quickly from foot traffic. Because it sits right at the base of the Valley's busiest trailhead, it makes an easy add-on before or after a longer hike rather than a destination that needs its own dedicated trip.
Frequently Asked Questions
What is a fen, and why is this one special?
A fen is a wetland that forms peat from decomposing plant matter, kept wet by steady groundwater rather than surface runoff. Fens are rare in California's dry Sierra summers, and this two-acre wetland is one of the few documented examples, sustained by snowmelt draining from the Glacier Point area.
How long does the boardwalk take to walk?
The loop covers roughly half a mile of flat terrain, so most visitors are through in well under 30 minutes — it's an easy stop rather than a full hike.
Where does the boardwalk start?
It's just west of the Happy Isles Nature Center at the east end of Yosemite Valley, the same trailhead area where the Mist Trail and John Muir Trail begin.
Can I walk out onto the fen itself?
No — stay on the boardwalk. The fen's soil and plant life are fragile and protected by split-rail fencing installed during a 2002 restoration.
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