Malebolgia

 was the 51st state of the United States of America, proposed around the year 2003. It was located in the southeastern mainland, formed from the division of a pre-existing state. Alistair Gordon Lethbridge-Stewart was sent there, after having helped establish the devolved parliament of Scotland, in order to offer the fledgeling state his experience and expertise.

The prime candidate for the first Governor was Brigham Elisha Dashwood III, an evangelist and politician who was also running the newly opened Brigham Elisha Dashwood Laboratory of Alternative Mentalities -- a mental hospital. Behind the scenes, the hospital was a front for the newly re-formed Hellfire Club, which was working to ensure Dashwood's election with the help of the demon Marchosias.

The Eighth Doctor and Charley Pollard became involved with the Laboratory and the Club, and subsequently exposed Dashwood's activities, ending his political career. (BFA: Minuet in Hell)

Behind the scenes

 * The exact geographic location of this fictional state is never made clear. However, when Lethbridge-Stewart makes his first report he says gives his report's time in EST time zone. Combining that with the accents of some of its apparent residents suggests the location to be somewhere in the southeast.
 * The name Malebolgia comes from Malebolge, the eighth circle of Hell, as described in Dante's poem The Divine Comedy. In that book, the circle was reserved for the souls of liars, cheats, and frauds.
 * There is no further mention of Malebolgia in any other context, suggesting that Dashwood's discredit may have killed the state's final ratification.