You have several trailhead options from the North:
Leavitt Lake: 3- 4 miles East of Sonora Pass on Highway 108, turn South on to a rough 4x4 road. In 1.75 miles you arrive at Leavitt Lake. Take the wide trail from the North side of the lake up to the top of the cliff to the South of the Lake.
Follow the PCT South down the hill. You can either take the jeep trail that makes a very large switchback or take the more adventurous single track that goes straight South. Stay right where the PCT turns East and head towards Big Sam in front of you. Approach Distance: 3.7 miles to Kennedy Creek
Sonora Pass: Park in the lot just North of HW 108 at the pass. Cross the HW and take the PCT South Past Leavitt Peak and on the ridge until you meet up with the trail that goes to Leavitt Lake below. See 2nd paragraph above for the rest. Distance: 9.75 miles to Kennedy Creek
Kennedy Meadows: Take the Kennedy Meadows turnoff West of Sonora Pass and drive to the end of the road. Follow the Trail South and East for 2.5 miles until the Relief Resevoir turn off. Stay left (East) and follow the trail SE until the Soda Canyon turnoff (6.8 miles). Stay left and follow the trail East past Kennedy Lake (7.9 miles) to where the trail heads South crossing Kennedy Creek and heading up Big Sam. 10.5 miles
Head South/ SW towards Big Sam. You will enter a large bowl on the North side of the mountain. The wide trail contours around the bowl from East to West. After this the trail swithbacks up towards the peak heading South. Snowfields often cover the trail on the north side of the peak through the summer. When I was there in late July, 2000, the trail was still covered with snow in several spots. Keep heading up until the trail tops out then head East to the obvious highpoint. The summit is only 100 feet or so from the trail. Enjoy the far ranging views including many Emigrant Peaks, Tower Peak, and Yosemite Peaks to the South. The trail continues down the South side of the peak towards Emigrant Pass if you choose to go on. About 2.2 miles and +1,050 feet from the bottom of the mountain.
Crampons and ice axe are necessary in Winter through Spring and beyond. Have enough water for the climb up and down.
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