The description below is the shortest thru-hiking route to complete the 12-Peak Challenge covering trails I’ve personally hiked and that I know are currently open with the least amount of miles spent on pavement instead of trails. Due to the additional mileage required to connect all the peaks, other peaks will be unavoidable or close to the trail and worth exploring as well. This route begins at the Cobb Estate and ends at Baldy Notch where the ski lift can be taken down to a parking lot. It covers about 91 miles with around 27,000′ of gain and 20,000′ of loss. For now, the description below just describes the route without breaking it down to potential backpacking or section hiking options. In the future (hopefully by May), I will add those options as well.
Starting from the Cobb Estate, follow the Lower Sam Merrill Trail to Echo Mountain. After exploring the peak, retrace your steps
After exploring the peak, retrace your steps to the first junction and take the Castle Canyon Trail to Inspiration Point and continue heading west to a junction with four other trails. Moving in a counter-clockwise direction, skip the first trail (leading down the Idlehour camp) and continue following the next option (Mt. Lowe Road). Take Mt. Lowe Road past the first junction (the East Mt. Lowe Trail) to the second junction (the West Mt. Lowe Trail, A.K.A. the Upper Sam Merrill Trail). Follow the West Mt. Lowe Trail to Mt. Lowe turning right and heading up a small spur trail at the junction with the Upper East Mt. Lowe Trail.
Return to the junction with the Upper East Mt. Lowe Trail, and take that trail by turning right and continuing around the north face of Mt. Lowe until you reach another junction. At that junction turn left and follow the trail heading north past the unmarked junction with a trail leading to Mt. Markham (a worthwhile side trip). Eventually, you will reach Mt. Lowe Road again at a junction which leads in four directions. Moving counter-clockwise, skip the first trail (which leads down to Eaton Saddle) and follow the second trail (unnamed but referred to here as the South San Gabriel Peak Trail for clarity) up to a junction with the San Gabriel Peak Trail. At that junction, turn right and head east up the summit trail to San Gabriel Peak.
Retrace your steps to the junction with the South San Gabriel Peak Trail and continue heading straight (west), including a brief distance along a paved road to the saddle with Mt. Disappointment (a short side trip). Turn right and continue heading north down the paved road to a junction with the Lower San Gabriel Peak Trail and follow that down to Mt. Wilson Road. From there, turn left and follow Mt. Wilson Road down 0.4 miles to Red Box. At Red Box, turn right and follow the Gabrieleno trail east to West Fork Campground passing junctions for Valley Forge Campground, the Valley Forge Trail, and the Kenyon Devore Trail along the way. From West Fork, turn left and take the Silver Moccasin Trail up to Angeles Crest Highway at Shortcut Saddle. Cross the highway and continue following the Silver Moccasin Trail to Mt. Vetter Road where you will turn left and follow the road up to Mt. Vetter.
Follow the road back down to the Silver Moccasin Trail, turn left and follow that trail through Charlton Flats, pass through the gate at the north end of Charlton Flats and follow the fire road down until it meets a junction and turn right (to continue following the Silver Moccasin Trail) up to Chilao. Continue following the Silver Moccasin Trail through Chilao and up to a junction leading to Horse Flats and turn left (west). From Horse Flats, turn left and follow the Mt. Hillyer Trail to Mt. Hillyer.
Either return back to Horse Flats the same way or follow a hiker’s trail to Horse Flats forming a loop and continue back to the Silver Moccasin Trail where you will turn left and continue past Bandito Campground to Three Points. At Three Points, turn right at the junction (leading away from the parking lot) and head down to Angeles Crest Highway. Cross the highway and head left (north) a short distance until you reach a trailhead sign for the PCT. Take the PCT up a short distance to another junction. Leave the PCT and follow the Mt. Waterman Trail past a junction leading to Twin Peaks to the Mt. Waterman Summit Trail and take that to Mt. Waterman.
Follow the summit trail back down to the junction and turn left to continue following the Mt. Waterman Trail east and then north down to Angeles Crest Highway. Turn left and follow the highway west to Cloudburst Summit. From Cloudburst Summit, there are four directions. Moving counter-clockwise, skip the first (the PCT), and the second (a dirt road), and take the third a short distance up to a junction and take the trail on the left up to Winston Peak.
Continue following the trail north down the north face of Winston Peak until you reach the PCT and take that down to the junction with the Burkhart Trail passing by Cooper Canyon Campground. At the Burkhart Trail, turn left and continue up to Burkhart Saddle passing the junction for the Rattlesnake Trail (A.K.A the PCT). From Burkhart Saddle, turn right and follow the hiker’s trail east along Pleasant view Ridge over Pallett Mountain and continue following the ridge east up and down along a faint hiker’s trail, past several bumps and up a short spur trail to Mt. Williamson at a junction where Pleasant View Ridge turns South.
Go back to the junction, turn left and follow Pleasant View Ridge south down to the PCT where you will turn left and follow that trail down to Islip Saddle. From Islip Saddle, cross Angeles Crest Highway and continue along the PCT to Little Jimmy Campground. At Little Jimmy, either hike through the campground and follow the trail up to the Islip Ridge Trail or continue along the PCT to Windy Gap passing by Little Jimmy Springs (a year-round water source that I would filter before drinking). Both options lead to the same stretch of trail that leads up to a junction where you will turn right and follow the summit trail to Mt. Islip.
Return down the summit trail and turn left at the junction (also retracing steps) until you reach Windy Gap. At Windy Gap follow the PCT up past the junction with the Hawkins Ridge Trail (leading to Middle Mt. Hawkins and South Mt. Hawkins), past another junction leading a short distance to Mt. Hawkins to the junction with the Throop Peak Trail (before reaching the Dawson Saddle Trail) and take that to Throop Peak.
Retrace your steps down to the PCT, turn left and continue following the PCT past the Dawson Saddle Trail and past a short hiker’s trail leading to Mt.Burnham to the junction at the Wally Waldron Tree. Turn right and follow the short distance to Mt. Baden-Powell.
Continue on the PCT by returning to the Wally Waldron Tree and hiking down to Vincent Gap. From there, cross Angeles Crest Highway and follow the PCT past Jackson Flat, Grassy Hollow, Inspiration Point, Blue Ridge Campground, Guffy Campground and the junction for the Acorn Trail. At the next opportunity, veer off the PCT and follow the road to the North Backbone Trail and follow that trail past potential short side trips to Pine Mountain and Dawson Peak ending at Mt. Baldy.
From Mt. Baldy, consider making the short trek to West Mt. Baldy to the south before descending down the Devil’s Backbone Trail past a potential side trip to Mt. Harwood down to Baldy Notch. At Baldy notch, take the ski lift down to parking.