Take the Georgetown exit off of Interstate 70. Drive through Georgetown and follow the signs for the Guanella Pass scenic byway through Georgetown. Drive 12 miles to the top of Guanella Pass (11,700') and park in one of the two large, paved parking areas on either side of the road. Mt. Bierstadt and The Sawtooth fill the view to the east. The Bierstadt trail starts near the parking area on the east side of the road. The upper parking area (on the west side of the pass) has restrooms.

Details:

Hike east down the Bierstadt Trail. There are wooden bridges that have been built recently so you don't have to walk through all of the muddy sections. The trail weaves through the willows and crosses Scott Gomer creek after over 1/2 mile. The trail has been improved over the past few years, so ignore the warnings that some guidebooks give about the willows. After crossing the stream, hike about 1/4 mile through the willows on the excellent trail. At 11,800', the trail begins to climb up a shoulder. You are out of the willows and the trail switchbacks to approximately 12,300' on the north end of the shoulder. The remaining route is now visible.

The trail goes left (northeast) and then curves around to the right (south) toward the slope ahead.. Gradually gain elevation as you continue south up the shoulder. Reach the base of the steeper slope near 13,000' and follow the trail as it climbs south and then southeast. The terrain on the slope is a bit more rugged and covered with boulders. If there is snow, you may have to make your own trail - just aim for the ridge above (southeast). Do not stray into the steeper terrain to your left (below the summit).   Reach the top of the ridge at nearly 13,800'.

The summit isn't visible from here but it's only another 250' of elevation gain.   Turn left, cross the remainder of the ridge, and begin your climb up through the boulders. This final pitch has some trail sections when free of snow. Keep climbing until the terrain levels out and stroll a bit further to the summit.