The Astoria Bridge is the last bridge before the mouth of the Columbia River into the Pacific, about 20 km away. She was the missing link to the U.S. To make Route 101 continuously passable along the West Coast of the USA between Olympia in the north and Los Angeles in the south. The southern end of the bridge is in Astoria (Oregon), the other end is at Point Ellice, a mountain promontory near the settlement of Megler, where the jetty for the ferry to Astoria used to be.
The river is around 6 km wide at this point, but mostly flat. The 12.19 m (40 ft) deep and narrow channel for ocean-going ships traveling to Portland runs directly in front of the town of Astoria; beyond it lie the Desdemona Sands, a sandbank that extends beyond the middle of the river and partially runs dry at low tide. Off the northern bank there are variable channels with slightly deeper water that can be navigated by smaller ships.