There are many wonderful hikes along the Historic Highway [1]. In addition to those described here, check out the National Forest Service’s Short Hiking Loops map, available free at the Multnomah Falls Lodge [2].
Links:
[1] http://www.moon.com/destinations/oregon/columbia-river-gorge/historic-columbia-river-highway-us-30
[2] http://www.moon.com/destinations/oregon/columbia-river-gorge/historic-columbia-river-highway-us-30/sights/multnomah-falls