The Hadley Trail is an ADA-accessible forested trail just over half a mile long in Beacon Rock State Park that takes you to a lookout point for Bonneville Dam and the Columbia Gorge. It can also connect you with the Hamilton Mountain Trail from the Beacon Rock Campground.
Starting out by campsite 11 in the campground, it is a rather unassuming beginning up a short set of easy switchbacks to where it levels out at a plaque on a large petrified stump that shares the history of the 1930's CCC built trail and Clyde Hadley, the first superintendent of Beacon Rock State Park. When the season is right, you will find wildflowers such as trillium and bleeding hearts to admire or salmonberries for the picking.
The trail then moves into mature second growth fir on a smooth grade as you weave through the trees and catch glimpses of the 848-foot basalt column of Beacon Rock. There is a junction for the Little Beacon Trail, which is also designed to be ADA and ends a quarter mile in at the base of Little Beacon Rock and views of the Gorge. It is definitely worth the side trip, especially if you are able to spot one of the critters that live in the shelter of the moss covered rocks.
The Hadley Trail continues on as it follows a gradual contour line to where the forest opens up of the south side of Little Beacon and runs by a picnic table and under the power lines, a quiet spot to stop before you come around to a larger viewing area and a sturdy bench to rest upon with views of the Bonneville Dam, Columbia Gorge and Hamilton Mountain at the junction for the popular Hamilton Mountain Trail.
Returning the way you came keeps you on ADA-accessible trail but heading down to the Hamilton Mountain trailhead you can loop back up the road to the campground (not ADA accessible).