Final answer:
The Inca civilization constructed a complex and extensive system of roads across the Andean mountains, facilitating the movement of armies, trade, and communication, which was crucial for maintaining control over their large empire.
Step-by-step explanation:
The early American civilization that constructed a vast system of roads that stepped up and down mountains is the Inca civilization. This impressive feat of engineering was unparalleled in the New World and rivaled the infrastructure of ancient Rome. The Inca road system facilitated the movement of armies, trade, and communication across the diverse terrains of their empire which included modern-day Peru, Ecuador, Chile, Bolivia, and northwest Argentina.
These roads were a key factor in the Incas’ ability to maintain control over their large and geographically diverse empire. Some parts of this network were built on pre-existing trails, but the Incas significantly expanded and improved the system to include suspension bridges, stairways, and even tunnels through mountains. The roads also played an important role in the dissemination of the Inca culture, as they helped integrate various peoples into the empire through easier access and mobility.
In the context of early civilizations, the development of such infrastructure is indicative of a complex societal organization with centralized control, specialization of labor, and resources to execute large-scale construction projects. The Inca civilization was a highly organized, agrarian society that demonstrated profound achievements in architecture, agriculture, and city-planning.