One of the most popular waterfalls in Oregon has to be Multnomah Falls. Located in the Columbia River Gorge; Multnomah Falls is a 45 minute drive outside of Portland. Once you get to the falls there is a parking lot right at the base of the falls and typically crowded with tourists.
Taking a road trip in Oregon?
Read: Best Places to Photograph in Oregon
This 2 tiered waterfall features over 700 feet of falls. Best of all there is a short hike to Benson Bridge which overlooks the fall.Multnomah Falls on Google Maps
Photos of Multnomah Falls
Here are Multnomah Falls pictures from my visit.