memory alpha

The MS I Colony was a Federation colony located in the MS system. This colony was located in the same sector as Ohniaka III and the New Berlin Colony.

In 2369, the colony was attacked by the rogue Borg led by Lore, but the attack was soon stopped when the USS Enterprise-D arrived at the scene. (TNG: "Descent")

In the 32nd century, MS I Colony was a Federation member. It was listed with other members on a video wall in the USS Athena. (SA: "The Life of the Stars")

This colony was only mentioned in dialogue.
According to Star Trek: Star Charts ("United Federation of Planets I"), in 2378, the MS 1 Colony was listed as a Federation member.