Final answer:
The 19th century saw advancements in transportation with the building of roads and canals, but the expansion of the railroad network had the most dramatic impact, revolutionizing travel and commerce.
Step-by-step explanation:
Throughout the 19th century, there were several significant developments in the area of transportation that profoundly impacted American society and its economic landscape. One key development was the construction of extensive road and turnpike systems, which facilitated overland travel and commerce. This was followed by a surge in canal building, including monumental projects like the Erie Canal, connecting regional markets and making the movement of goods more efficient. However, it was the introduction and expansion of the railroad network that truly revolutionized transportation, drastically reducing travel times and enabling rapid economic growth. By connecting port cities with the interior, railroads formed the backbone of a national market system and fostered the spread of the telegraph, further uniting distant regions of the country.