Final answer:
The chief rivers related to free trade in the historical context are primarily the Mississippi and Missouri Rivers. These waterways were the subject of treaties like the Treaty of Ghent and were crucial for commerce and expansion of the U.S. Sovereignty over such rivers enabled economic growth and facilitated international trade.
Step-by-step explanation:
The "chief rivers" mentioned appear to be primarily related to significant historical agreements and treaties that facilitated or impeded free trade and commerce, such as the Mississippi River and the Missouri River. During the period after the War of 1812, the Treaty of Ghent and subsequent agreements like the Rush-Bagot Agreement sought to address unresolved issues including navigation and trade along these rivers. The Mississippi River was particularly crucial as it was closed to American traffic by the Spanish, impacting Southern trade through New Orleans. Negotiations led by John Jay attempted to secure navigational rights, but initially failed due to Spanish intransigence and domestic opposition. The importance of riverine trade is also exemplified by explorations to seek direct water communication for the purposes of commerce, as in the case of the Missouri River that aimed to connect with waters leading to the Pacific Ocean. Furthermore, Article VIII of a separate treaty promised that both Americans and British subjects would always be permitted to travel the full length of the Mississippi River.
These rivers were vital as they were natural conduits for trade and movement of goods in an era when overland transportation was inefficient and costly. The push for sovereignty, control over territory, and access to these waterways was intertwined with the economic health and expansion of the United States.