My boat lifted and fell in the gentle ocean swell a few miles seaward from Cape Disappointment off the mouth of the Columbia River. Although the summer morning was calm, my exposed offshore position made me nervous. I was in a small boat I had built for a journey up the Columbia, not for a voyage on the open ocean. But the journey had to begin from the sea if I was to approach the river, cross its bar, and then travel upstream as a sailing ship had done nearly two centuries ago to begin the first chapter of the river’s recorded history.

An ebbing tide had carried me away from the coast, through the ship channel, and out past the broken ends of the two stone jetties that define the outer ramparts of the river mouth. Sea birds skittered before me and then resettled on the sea in clusters, preening themselves as they bobbed up and down ons the ocean waves. A distant bell buoy clanged in the slow roll of the long Pacific swells. There were no other boats or ships around.

Turning the boat, I looked back at the coast. To the north, the descending spine of Cape Disappointment ended in a steep cliff. To the south, the low sands of Clatsop Spit formed the blur of a distant beach. The backdrop of dark Washington hills seemed to tie the land together in one long, unbroken shore. Were it not for the jetties and the line of the buoys marking the channel, I would have lost sight of the river entrance.

I tried to picture the Columbia as it must have appeared to an eighteenth-century maritime explorer, when sandbars filled the river mouth: swells, breaking on those bars, would have appeared to him as a continuation of the surf that broke north and south of the river in an uninterrupted white line. My short sea voyage had already made clear to me why the Columbia was the last of the world’s great rivers to be discovered. To that eighteenth-century captain, the Columbia River was nearly invisible.

Though unseen, it had a name: the River of the West. A geographical theory of the time held that from a collective height of land somewhere on the continent fell four rivers, one for each cardinal point of the compass. There was the River of the East (the St. Lawrence), the River of the South (the Mississippi), and evidence of the River of the North (now called the Mackenzie). The missing link was the River of the West. If it could be found, the seas washing the continent would be linked by an interior waterway wonderfully convenient for commerce.

The Columbia was first noted by Spanish captain Bruno de Hezeta as he was returning in his ship Santiago from an exploring voyage north along the coast in 1775. He wrote in his logbook on August 17, 1775: