What was one major transportation development mentioned that facilitated westward expansion?

The National Road played a crucial role in facilitating westward expansion in the early 19th century. Constructed starting in the 1810s, it became the first major improved highway in the United States, connecting the eastern states with the western frontier. This road provided a reliable route for settlers traveling west, bringing goods and new ideas into the developing territories. It significantly reduced travel time and enhanced accessibility, making it easier for families and entrepreneurs to move westward in search of land and opportunities. Its construction was part of the broader push for infrastructure that would support the nation's growth.

While the Mississippi River system, the Transcontinental Railroad, and the Pony Express were also important in terms of transportation and communication, their impacts came later or in different contexts. The Mississippi River system was essential for trade and transport but did not directly facilitate the physical movement of settlers in the same way as the National Road. The Transcontinental Railroad, completed in 1869, was a later development that connected the east and west coasts but came after the National Road had already established a critical pathway for westward migration. The Pony Express served mainly as a mail delivery service and was operational for only a short period in the 1860s. Thus, the National Road stands