The route started in Waterfront Park went down to Lake Oswego just past Elk Rock. Per informational cards provided that's where the Willamette River is at its deepest. We turned around near a rail bridge, came back to downtown and passed under the Morrison Bridge for a view of the city before returning to shore. I took this picture near the rail bridge, and some other pics of the rail bridge that didn't really turn out because it was so dark.
We passed under 5 bridges, only one of which had to be raised (twice!) for us, the Hawthorne Bridge. Everyone on the boat was pretty excited about stopping traffic. And there were plenty of excited "I'm on a boat" proclamations throughout the evening, from both the musicians & the passengers.
The city as seen from the water at night with all the reflections is pretty amazing, especially with good, local, live music!
Update: Google posted a set of pictures from the event here.