Boreal III was the inhabited third planet in its system.
In 2367, the transport Kallisko from Boreal III was attacked by the Crystalline Entity with all hands lost in the attack. The last action of the captain of the ship was to ask the USS Enterprise-D to inform their people on Boreal III. (TNG: "Silicon Avatar")
In 2371, the location of Boreal III was labeled in the star chart Data and Picard were studying in stellar cartography aboard the USS Enterprise-D. (Star Trek Generations, display graphic)
Next to the identifying label in the chart from Generations, there was the number "0358".