Gamma Canaris N was an inhabited planetoid, in the Gamma Canaris region. The location of Gamma Canaris N in the Milky Way Galaxy was depicted on a Federation star chart in 2293. (TOS: "Metamorphosis"; Star Trek VI: The Undiscovered Country, production art)
In the faked computer records of Commander Keiran MacDuff, it was stated he was born there on September 27th, 2334. (TNG: "Conundrum")
According to to Startrek.com, Star Trek Concordance and Gold Key Comics Star Trek issue 49 A Warp in Space, Gamma Canaris N was the name of Companion's homeworld.  
"The Explored Galaxy" was a map of charted space in the Alpha Quadrant. Gamma canaris N was located between the Tholian Assembly
. Both locations were identified in DS9
: "The Search, Part II
", "Call to Arms
" as being located in the Alpha Quadrant. This chart, first seen chronologically in Star Trek VI: The Undiscovered Country, was also seen in several Star Trek: The Next Generation and Star Trek: Deep Space Nine episodes set in the 24th century, from the year 2364 to 2370. These were TNG: "Conspiracy", "The Measure Of A Man", "The Emissary", "The Mind's Eye", "The Game", and DS9: "In the Hands of the Prophets", "Cardassians".