Missouri Moseley

Missouri Moseley is a psychic residing in Lawrence, Kansas. She is a long-time ally of John Winchester's.

"Home"
When the brothers return to Lawrence following a premonition that Sam has, they search the phone directory for psychics. Dean stumbles upon her and quickly remembers that his father had mentioned Missouri in his journal. So far, Dean had thought that John had meant the state Missouri.

With the help of Missouri, Sam and Dean try to banish the poltergeist which has taken up residence in the Winchesters' old home. However, it is Mary's spirit that eventually succeeds in defeating the poltergeist.

Near the end of the episode, it is revealed that John has been at Missouri's the whole time his boys were in Kansas, but has reluctantly kept himself hidden. Missouri finds it strange that Sam could have premonitions of his old home but could not sense his father in the next room.

Trivia

 * Eric Kripke revealed at Paley Fest that Missouri was intended to return in the Season 1 finale to help Sam and Dean, but because Loretta Devine couldn't do it, the character of Bobby Singer was created instead﻿.
 * Missouri has an expanded role in Supernatural The Animation, appearing not only in "Home" but also in "Rising Son" and the two-parter "All Hell Breaks Loose" (where she fills the role of Ellen in the live action series).

Season 1

 * "Home"

Season 7

 * "The Mentalists" (mentioned only)