Final answer:
By 1850, the extensive system of railroads became the dominant transportation network in America. Rails greatly improved efficiency in transport, trade, and communication, aiding in the development of a national market system and signifying a major shift from canals as the main transport avenues.
Step-by-step explanation:
By 1850, the American transportation network mainly ran on an extensive system of railroads. This transformative period in American history is marked by the transportation revolution that included the advent and expansion of the steam locomotive, which transformed the economy and social landscape of the nation. Previous to railroads, canals served as the primary means of commerce and trade within the country. However, with the expansion of the railroad infrastructure, which began in the 1830s, and the associated technologies such as the telegraph, an interconnected network that fueled the emergence of a national market system was established. Transport costs decreased and the movement of goods and people became faster and more efficient, pushing the United States towards modernity.
The federal government and the states funded grand infrastructural projects to build extensive roads, canals, and especially railroads to support this transformation. The railroad industry, spurred also by competition among states for advanced transportation systems, quickly became America's first 'big business' and led to the greater development of related industries such as iron, wood, and coal. The efficiency of rail transport drastically improved internal migration, trade, and communication, effectively shrinking the vast distances within the country. By the time of the Civil War, over thirty thousand miles of railroad track had been laid, signifying the shift in dominance from canals to rail transport, and marking the successful binding of the vast Republic.