Take the Santiam Pass Highway from Sisters west through the Cascades. You'll see a pullout on the left for the Iron Mountain Trailhead. After parking, retrace your steps heading back east by a quarter of a mile and you'll see the trailhead for Cone Peak on your left.
Allow about an hour or 75 minutes to hike to the top. If you're hiking up before dawn, bring a headlamp. Tripod is a must for the long exposures of dawn's low light. Bring mosquito repellent and ND grad filters, or be ready to take multiple exposures to balance the brightness of sky and terrain.
This is a shot taken at dawn from a wildflower meadow on Cone Peak. Across the way, the rising sun is illuminating Iron Mountain in the Cascade Range of Central Oregon. I waited patiently, just me and the mosquitoes that were avidly looking for breakfast, for the sun to light up the peak of Iron Mountain before pressing the shutter.