Special Thanks to CharlesD, the original author of this page.
Atlantic Peak, when it is mentioned at all, is usually mentioned in the same breath as its loftier, pointier neighbor to the north, Pacific Peak. They are often climbed together and both are on the list of Colorado's "Highest 100" peaks. With its place on this list at #87, Atlantic is a very worthy destination in its own right. There is an easy route up the east side and a more exposed challenging route up the west ridge, as well as a snow route on the east face. The traverse south from Atlantic to Fletcher Mountain appears insanely rugged and toothy, but has been climbed by some hearty souls; the route is said to go at 5.7 and is included in Dave Cooper's book "Colorado Scrambles". Atlantic Peak was for years just a nickname, and most maps will still show it unlabeled as "PT 13841", the USGS does, however, recognize the name Atlantic Peak officially as of a few years ago.
Atlantic is commonly approached from the Mayflower Gulch Trailhead on the west or the McCullough Gulch trailhead on the east.
Mayflower Gulch: The trailhead is located approximately six miles south of Copper Mountain and I-70 and 4 miles north of Fremont Pass. There is a large parking area on the east side of the road. From the parking area, a rough 4WD road heads up the valley 1.5 miles to the ruins of the Boston Mine. This road is passable in season by high-clearance vehicles. Beware, however, that it is narrow and parking is limited along its length.
McCullough Gulch: This trailhead is considerably more remote than Mayflower. Take CO-9 eight miles south of Breckenridge or two miles from Hoosier Pass. Turn west on County Road 850 and an immediate right onto a dirt road. This is the standard approach for the popular Quandary Peak and parking along the road may be at a premium. Continue two miles north to the trailhead. This road is not often plowed in the winter and may be impassable.
No permits necessary but there is an informal agreement that no more than 1023 climbers may occupy the summit at any given time.
Atlantic Peak is included in the Hidden Gems Wilderness campaign, if passed by Congress the surrounding areas (including Atlantic's summit and McCullough Gulch) would be part of a new wilderness area to be designated "Tenmile Wilderness". For more information, click here. Note, the Mayflower Gulch Road which accesses the Boston Mine would be unaffected and remain open to motorized/mechanized travel.
Atlantic is a good casual hiking destination in the summer and fall. Hikers should be aware, however, that there are no good escape routes from the west ridge in the event of lightning. It is continuous and exposed and bounded by steep scree and small cliffs most of the way down.
Winter ascents require snow gear such as snowshoes, crampons and ice axes. The ridge develops some large cornices and should only be climbed in stable conditions.
Winter conditions may continue well into spring with the final bits of snow at the higher altitudes melting out in mid-late summer. With snow on the ridge an ice axe is recommended as the lingering cornices may require an exposed traverse along one side.
There are some very unofficial campsites near the Mayflower Gulch trailhead. I don't know if these are officially sanctioned or not, but they clearly see some activity. Caveat emptor.