Yorktown-class carriers were starships in service first to the Earth Starfleet and then the newly-formed United Federation of Planets Starfleet in the 22nd century. (The Starfleet Museum)
The prototype USS Yorktown (NCC-395) launched on May 23rd 2155. The ship could surpass Warp Factor 5.7 and had twice the armament of an NX-class starship. These vessels also had a crew of 147 and were still in active service by 2270. These vessels were retired sometime after.
Vessels of this class were first on active duty during the Earth-Romulan War. Aboard them were embarked Minotaur-class fightercraft.