The association of the Mason-Dixon Line with chattel slavery, plantations, and mosquito-borne disease is not a coincidence. Tobacco and cotton did not grow in the northern states; therefore, the plantation-slave system was nonexistent. These crops grew in the warmer climes of the South, where mosquitoes thrived. These plantations also needed slave labor to produce profit. The imported slaves added to the robust mosquito landscape by introducing falciparum and yellow fever, and perhaps vivax.
