"We examine portage sites in the U.S. South, Mid-Atlantic, and Midwest, including those on the fall line, a geomorphologic feature in the southeastern U.S. marking the final rapids on rivers before the ocean. Historically, waterborne transport of goods required portage around the falls at these...

According to economic theory, imbalances in trade flows affect transport prices because (some) carriers have to return without cargo from the low demand region to the high demand region. Therefore, transport prices in the high demand direction have to exceed those in the low demand direction....