The state of Mississippi was the 32nd most populous and 32nd largest state in America before the outbreak
Not a lot is known about Mississippi during the outbreak. It can be assumed that it followed the example of California, with state and local police being among the first responders, with these first responders being joined by military units if and when a state of emergency was declared. (N.B. It is unknown at what point Operation Cobalt became 'official' government policy after the fall of California. It is therefore possible that military units were deployed alongside Emergency Services.
Morgan Jones arrives in Mississippi by accident, after falling asleep in the back of a truck while taking shelter from a storm in Texas. While there, he comes across two survivors, Wendell and his sister Sarah.