Final answer:
The largest social class in New Spain was made up of mestizos and Native Americans due to their significant numbers resulting from intermingling and native population before the Spanish conquest, unlike the smaller numbers of peninsulares and creoles who held power.
Step-by-step explanation:
The social class in New Spain that was the largest consisted mainly of mestizos and Native Americans. The mestizos were of mixed European and Native American heritage, and this group expanded rapidly due to the intermingling of Spanish settlers and the indigenous population. On the other hand, the Native Americans made up a significant proportion of the population as they were the original inhabitants of the region prior to the Spanish conquest.
Despite the presence of the peninsulares and creoles who held political and economic power, it was the diverse and sizable mestizo population along with the Native Americans, who constituted the majority in the colonial society. This was also due to the fact that many peninsulares and creoles did not arrive in large numbers or have as high birth rates compared to the mixed and indigenous populations.
The caste system in New Spain was quite complex and featured multiple levels that were defined by heritage and race. At the top were the peninsulares, followed by the criollos, and then increasing numbers of mestizos, mulattos, and other mixed-race groups like zambos, with Native Americans and enslaved people at the bottom.