How did railroads change trade along the Columbia River?

Railroads fundamentally transformed trade along the Columbia River by ending the transportation monopoly previously held by river-based routes. Initially, the river served as the primary artery for commerce, with trade dominated by Portland through a combination of river steamers and connecting stages.1

The impact of railroads occurred in several stages:

• Early Circumvention: Because the river contained numerous difficult rapids, the first railroads were built as short portage lines—such as a 1.5-mile mule-drawn tram—to bypass the most treacherous sections.1
• Expansion of Connectivity: The completion of a rail line from Portland to Walla Walla in 1882, followed by a line connecting St. Paul to Portland and Tacoma, significantly expanded trade reach.1
• End of Monopoly: In 1887, the Northern Pacific Railway reached Tacoma directly over the Cascade Range, which effectively broke the Columbia River route's monopoly on the region's heavy agricultural and mining trade.1