Mount Islip Hiking Guide
Mount Islip is the San Gabriel high country at its most approachable: a real 8,000-foot summit reached by a well-graded trail through Jeffrey pine and white fir, topped by the stone foundations of an old shelter and a view that runs from the desert to the ocean. It sees a fraction of the traffic that Baden-Powell gets a few miles east, and it stays genuinely cool through summer, making it one of the better July escapes from Inland Empire heat.
Access and Route Options
The most common start is Islip Saddle on Angeles Crest Highway, where a large lot and vault toilets sit right at the trailhead. An Adventure Pass is required. From here the trail climbs through forest and joins the Pacific Crest Trail for a stretch before branching to the summit. An alternate approach starts from the Crystal Lake area to the south and is longer with more gain. As with everything on this stretch of SR-2, seasonal highway closures determine whether the trailhead is reachable at all — check before you drive.
The Climb
The grade is steady and civilized, built as a proper trail rather than a use path, with switchbacks that keep the pitch reasonable. You gain roughly 1,600 feet over a bit more than three miles, mostly under forest cover, which is a rare luxury in Southern California hiking. The tread is duff and decomposed granite, easy on the feet. The final push to the summit ridge opens up and the trees thin, and the last stretch is more exposed to sun and wind than everything below it.
The Summit and the Ruins
The top holds the stone foundation and chimney remains of a shelter that once stood here, now a scattered ruin that makes an excellent windbreak for lunch. The view is the real draw: the Mojave stretching north beyond the crest, Mount Baden-Powell and the higher peaks to the east, and the basin haze to the south with the ocean beyond on a clear day. Because Islip sits slightly apart from the main ridge, the panorama is more complete than from summits buried in the crest.
Weather at 8,000 Feet
The altitude changes the calculus entirely. Summer temperatures here can be twenty-five degrees cooler than the San Gabriel Valley, which is exactly why the peak is worth the drive in July and August. It also means afternoon thunderstorms build quickly and the summit is an exposed place to be caught out — plan to be off the top by early afternoon in monsoon season. Snow lingers here well into spring, and in winter the highway closure usually settles the question for you.
Dogs, Water, and Preparation
Leashed dogs do well on this trail, with shade for most of the climb and cool temperatures, though the elevation affects dogs too — a dog that cruises a coastal hike may tire noticeably faster up here. There is no reliable water on the route, so carry everything, and bring more than the mileage suggests because dry high-altitude air is deceptively dehydrating. A wind layer is worth packing year-round; the summit ridge catches wind that the sheltered climb never hints at.
Hiking tips for Mount Islip
- Confirm Angeles Crest Highway is open before driving; seasonal SR-2 closures put Islip Saddle out of reach for a good part of the year.
- Use this peak as a summer heat escape — the summit routinely runs twenty-plus degrees cooler than the San Gabriel Valley floor.
- Be off the exposed summit by early afternoon from July through September, when monsoon thunderstorms build fast over the crest.
- Pack a wind shell even on warm days; the sheltered forest climb gives no hint of what the summit ridge is doing.
- Carry all your water and then some — at 8,000 feet the dry air dehydrates you faster than the moderate mileage would suggest.
Nearby trails to explore
- Mt Baden-Powell
- Big Horn Mine
- Crystal Lake Trails
Hike this trail with TrailMates
Mount Islip is the high-country summit most Southern California hikers have never done. Use TrailMates to find people organizing Angeles Crest trips while the highway is open, share the drive up SR-2, and swap beta on which trailheads are currently reachable. Download the TrailMates app to connect.