What is the historical vector for malaria east of the Rocky Mountains?

The historical vector for malaria east of the Rocky Mountains is Anopheles quadrimaculatus. This species of mosquito has been identified as the primary carrier of the malaria parasite in the eastern United States. Anopheles quadrimaculatus is particularly adapted to the temperate environments found in this region, making it effective at transmitting malaria to humans.

This vector is well-documented in the context of the historical presence of malaria in the U.S., especially before the disease was significantly controlled through public health measures. In contrast, while Aedes aegypti is known for transmitting diseases like dengue, Zika, and yellow fever, it is not a vector for malaria. Culex pipiens primarily transmits West Nile virus and is not associated with malaria transmission. Anopheles gambiae, although an important vector for malaria in many parts of Africa, is not relevant in the context of the historical transmission of malaria in the eastern United States. Thus, Anopheles quadrimaculatus stands out as the correct answer for the historical context provided.