The answer is Voluntary exchange
The correct answer to this open question is the following.
Unfortunately, you did not attach any text, article, context, or reference to know who the authors are and what they are specifically talking about.
However, trying to help you, we can comment on the following.
One of the most impressive things that some authors mention when they talk about Cahokia and led archaeologists to conclude that it was a major trading center, was the large mounds built in that location that could have served to store food or goods that were part of the things they traded.
Cahokia was an ancient Native American settlement located in the territory of what today is Illinois, approximately in 700AD. They were talented people capable of constructing those amazing and large mounds. Archeologists say that this place was the largest city north of México before the arrival of Christopher Columbus. They were known to be good traders that used the Mississippi River to navigate, transport people, and goods to other regions.
Eleven years after the outbreak of the Mexican War of Independence, Spanish Viceroy Juan de O’Donojú signs the Treaty of Córdoba, which approves a plan to make Mexico an independent constitutional monarchy.
In the early 19th century, Napoleon’s occupation of Spain led to the outbreak of revolts all across Spanish America. On September 16, 1810, Miguel Hidalgo y Costilla, a Catholic priest, launched the Mexican War of Independence with the issuing of his Grito de Dolores, or “Cry of Dolores” (Dolores referring to the town of Dolores, Mexico). The revolutionary tract called for the end of Spanish rule in Mexico, redistribution of land, and racial equality. After some initial successes, Hidalgo was defeated, captured, and executed. However, he was followed by other peasant leaders, such as José María Morelos y Pavón, Mariano Matamoros, and Vicente Guerrero, who all led armies of native and racially mixed revolutionaries against the Spanish and the Royalists.
Ironically, it was the Royalists—made up of Mexicans of Spanish descent and other conservatives—who ultimately brought about independence. In 1820, liberals took power in Spain, and the new government promised reforms to appease the Mexican revolutionaries. In response, Mexican conservatives called for independence as a means of maintaining their privileged position in Mexican society.
In early 1821, Agustín de Iturbide, the leader of the Royalist forces, negotiated the Plan of Iguala with Vicente Guerrero. Under the plan, Mexico would be established as an independent constitutional monarchy, the privileged position of the Catholic Church would be maintained, and Mexicans of Spanish descent would be regarded as equals to pure Spaniards. Mexicans of mixed or pure Indian blood would have lesser rights.
Both were allied victories
