The USS John Muir (NCC-1732) was a 23rd century Federation starship operated by Starfleet.
In 2293, the John Muir was receiving a system upgrade at Starbase 24. The ship was named on a Starship Mission Assignments chart on the USS Enterprise-A bridge. (Star Trek VI: The Undiscovered Country)
The John Muir was named after the renowned environmental advocate who was largely responsible for the creation of Yosemite National Park. The ship itself was not mentioned in dialogue, but was listed on a starship status display that was seen on the Enterprise-A. The information came from the Star Trek Concordance.
According to a ship listing included in the plans, and not seen in the extended cut of the movie, the ship's commanding officer was S.C. Jaffe. The ship's captain was named after the sixth movie's second unit director Steven-Charles Jaffe. [1]