For access to the standard route up Mackay Peak from Arco, Idaho, drive north on Highway 93 for rougly 25 miles until reaching the town of Mackay. Turn left (west) on Main Street in downtown and follow the road until it becomes the Rio Grande Road.
This improved dirt road will lead to the base of Mackay Peak's east face within a matter of minutes. From here, several roads will branch from the main road. Four wheel drive is recommended at this spot as the roads deteriorate in condition. Take a good local TOPO map and drive as far as you can onto the northern slopes of Mackay Peak.
Once you have begun hiking higher onto the slopes, an more obvious road will come into view that switchbacks gradually up to the north ridge of Mackay Peak. Follow this road with good tread until that ridge at just above 9,400'.
Then turn south and hike up the high and gradual slopes until reaching the last push to the summit.
Climb a couple hundred feet through mixed evergreens and granite croppings until coming to the obvious point where the route becomes a boulder hop. Skirt one last large outcropping on the east and scramble easily to one of the three summits, all of which can be accessed via Class II scrambling but can be made fun by throwing in a little climbing.
No essentialy gear required. It is highly recommended to bring a good topographical map as the presence of numerous roads may be confusing.
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