From the passenger car parking at 10,460 ft., hike along the road as it crosses to the west side of Cunningham Creek and then heads uphill and south. In a little over a half mile, you'll arrive at the 4WD parking and the end of the road which again crosses back over Cunningham Creek. A gate prevents further driving, but the vehicle track continues some distance before becoming more of a trail. Not far up from the upper trailhead parking, the creek passes through a narrow chasm of either granite or metamorphic rock and presents quite a tumultuous sight. At about 11,620 feet, will be the campsite we mention in the trailhead description. It's on the slope of a hillside that runs between the two major forks of Cunningham Creek. On this unlikely looking slope, there are some tall trees and some flat spots to pitch a tent.
The main trail to Highland Mary Lakes turns west here following the stream, then turns south again to follow the main stream that drains one of the first lakes. A few hundred yards before arriving at that first lake (12,100 ft), cut right (west) up a steeper slope and gain the south flank of a mostly tundra-covered, broad ridge that's east of the Mt. Rhoda summit (UN13,402). This 13er summit is unranked. Follow the ridge west and contour into a basin on the south side. Stroll on up the lush basin admiring the wildflowers (if you're there at the right time) and at the head of the basin, either hike up the SE flank of Mt. Rhoda or walk to the saddle south of the summit. If you go to the south saddle, you may wish to contemplate hiking south first to Whitehead Peak (unranked), and then on to UN13,109, before turning around and going back to Mt. Rhoda. The summit is capped by a minor cliff band that can be avoided on the west side.
Enjoy the magnificent view of the Grenadier Range to the south, then make a decision as to whether or not to continue to Mountaineer Peak, a half hour stroll north along the ridge. To descend, head back as you came and take some extra time to walk around some of the Highland Mary Lakes. A side hike to Verde Lakes will offer even more spectacular photo ops of the Grenadiers.