In what year did the USMC establish its first aviation unit?

The establishment of the first aviation unit in the United States Marine Corps occurred in 1913, making this the correct answer. This early unit, known as the Marine Corps Aviators, marked a significant evolution in military operations and the role of aviation in warfare. The formation of this unit demonstrated the foresight of military leaders at the time, recognizing the potential of air power in supporting ground operations. This initiative laid the foundation for what would become a critical capability for the Marine Corps and modern warfare as a whole.

The other years reflect important moments in aviation history, but they do not correspond to the formation of the first Marine aviation unit. Each of those years saw various developments in aviation, whether in civilian aviation or other military branches, but it was in 1913 that the Marine Corps officially launched its own aviation efforts.