The sign does say that it's 2 miles. TOPO and other maps say that its a mile. I feel like its probably closer to one than two but might feel longer because it's steep.
From the large pullout parking area on the north side of Hwy. 103, look across the road and search for a three-foot high cement marker with the number 290 on it. This is the start of the Chief Mountain trail. The trail starts steeply and immediately switches back from heading sourheast to west.
Another option is to continue west on Hwy 103 for another mile to where another branch of the Squaw Peak road intersects the highway. Hike or ski east up this gentle road for one mile to intersect the Chief Mountain trail and turn right to continue to the summit.
The sign posted where the trail crosses Old Squaw Pass road says it's 2 miles to the summit (most sources say it's 1 or 1.5 miles). After walking it, I would say it's closer to 2 miles.