The Galen IV colony was a Federation colony on the planet Galen IV where, in 2353, Jeremiah Rossa was born. The area it was in included a forest.
Four years later, the colony was attacked by the Talarian militia during the Galen border conflict. During the battle, Jeremiah's parents were killed and he was adopted by Endar, a Talarian officer. (TNG: "Suddenly Human")
This colony was only mentioned in dialogue.
According to the Star Trek Encyclopedia, 4th ed., vol. 1, p. 292 , Galen IV was a Class M planet.
According to Star Trek: Star Charts ("United Federation of Planets I"), in 2378, Galen IV was listed as a Federation member.