Make no mistake: unless you are an experienced hiker or a triathlete, or a trail-running…read moremarathoner, or maybe a Jack Russell Terrier who just had an espresso shot, this is a challenging hike... but mile for mile, it is a great way to spend a day exploring several different ecosystems within the San Gabriel mountains.
Starting in Eaton Canyon, there are at least three different entry points-- two of them along Altadena Drive that runs adjacent to the canyon, and the highest entry off Pinecrest Dr.--to begin your journey. Eaton Canyon has a well-travelled dirt trail through the lower scrub of yucca, buckwheat, and sage in the mostly dry boulder field of the canyon bottom. If you enter at Pinecrest, you will bypass this, cut about a mile off the trip, and use the bridge to access the Mt. Wilson Toll Road.
The Toll Road is an historic pathway dating back to the 1890s. Today, the "toll" portion of the title is a misnomer, as the trail is free for pedestrians, cyclists, and horses. The Toll Road is a steady uphill climb and mostly unshaded for about 2.5 miles to Henninger Flats. At last Check, there was no potable water at Henninger (or anywhere else in this hike) so plan your hydration according to weather and your needs.
Henninger features a nature center (seasonally open), picnic and overnight camping facilities, and a tree farm. Continuing up the toll road about a mile past Henninger, the main toll road makes a switchback turn to the right... and easy-to-miss the first time on the LEFT your path continues to Idlehour Camp, beginning with a small wooden bridge. You'll notice the trail narrows significantly from here on to Inspiration Point. The trail climbs a little, then you start your descent into upper Eaton Canyon. As you go, you'll notice fewer signs of humanity, except maybe the erosion controls on the trail, as well as some pretty views of Mt. Wilson, Mt. Baden Powell, and some of the decomposed granite rock formations above Eaton Canyon. Be careful of overhanging poison oak in this area. This is also likely the buggiest part of the trip, with plenty of black flies to keep you company. If you have a head net... now's the time.
Towards the bottom, you'll discover a very different Eaton Canyon: you are now a couple of miles above the lower waterfall where weekend canyon visitors bring lawn chairs, ice chests, and loud Bluetooth speakers. Instead of yucca and prickly pear cactus on a dry creek bed, you'll likely find flowing water under a canopy of oaks and bay trees. In season, wildflowers are abundant... but watch your step, as there is a lot of poison oak here, too. Some primitive campsites here feel like they're hundreds of miles from civilization, when really, you're only about 5. Stop here, sit, and enjoy what Eaton Canyon is SUPPOSED to be. Have a drink of water.
Heading essentially north from Idlehour camp, more or less parallel to the creek, the hiking trail is slightly broken in places but pretty easy to recover. The trail will continue up the west canyon wall of Upper Eaton, climbing through chaparral, into and through oak scrub, a pine forest, and mature stands of manzanita. As you climb, the trail softens a bit underfoot in the forest duff, and if you're an old trail runner like me, you will love this part the best. Depending on seasonal winter rains, April or May can be exquisite for wildflower viewing in this area.
Approaching Inspiration Point, you will pass through an area that burned relatively recently. The narrow single track will join a wider trail called Mt. Lowe Rd. and there is a small sign listing Mt. Lowe and other spots up the way. If you continue more or less straight, you're on the Sam Merrill trail... and going the wrong way.
When you hit the crossroads, make a strong left on Mt. Lowe Rd. and walk up the last stretch of wide dirt road to Inspiration Point. You've made it! Take a seat, relax, and enjoy the view.
Return the way you came, or you can take the Castle Canyon trail to the left of the interpretive center at the top (rocky and steep in places, but very pretty and sometimes shaded) or the Sam Merrill Trail (a little more forgiving, but a little slippery in places if you have bad shoes) to Echo Mountain, then down to the top of Lake Avenue, and walk streets through northern Altadena back to your car at Eaton Canyon (which will add a couple of miles to your trip on the loop...making it something like an 18 mile loop!)
This is one of my favorite hikes in Southern California, and it will provide most of us with a great challenge. Try it in different seasons for different experiences. As a reminder, always file a "hiking plan" with someone back home... just send someone a text with your route and times so that if something unexpected happens, responders will know where to look. Be safe, take extra water, leave only footprints (don't litter), and have fun out there!