Final answer:
Scott wishes to build a bridge across the Missouri River to connect the nation in a historically relevant way, reflecting the Missouri's importance in continental exploration and commerce.
Step-by-step explanation:
The river that Scott wants to build a bridge across, which will connect the nation together like never before, is the Missouri River. This ambition is likely rooted in the historical significance of the Missouri River as a means of exploration and travel across the continent. The exploration of the Missouri and its adjoining rivers played a crucial role in commerce and the expansion of the United States to the West.