Mississippi

 Mississippi was a state of the United States of America.

During a dream Benny once had, Mississippi was implied to be relevant to Martin Luther King, Jr. The dream involved a Dalek, a Cyberman, a Sontaran and Kadiatu Lethbridge-Stewart. During the course of it, Grinx the Sontaran said, "I have a dream that little Sontarans and little Rutans will one day walk through the streets of Mississippi, hand in tentacle…" (PROSE: The Also People)

The Eleventh Doctor, Alice Obiefune and John Jones visited Mississippi in 1931. (COMIC: What He Wants...)

Behind the scenes
The state of Mississippi has received almost no attention in DWU fiction, not even in American Civil War stories like Blood and Hope. The river, however, is a more frequent topic of conversation.