Ixodes, or black-legged tick. This is the "deer" tick. Transmits Lyme Disease, Ehrlichiosis, and Babesiosis (Babesia). Originally, the belief was, that a new tick, Ixodes Dammini, was the vector for Lyme Disease. Research completed in 1993 found that they were actually the same tick.
Amblyomma, or the Lone Star Tick, transmits Ehrlichiosis, Rocky Mountain Spotted Fever,
Dermacentor, or American Dog Tick, can transmit Colorado Tick Fever, Rocky Mountain Spotted Fever.
Tick distribution map done by the CDC. To save on downloading time, you can view it here