Team Fortress 2 launched with six official maps, expanded to eight with the release of cp_badlands and pl_goldrush. Additionally, the cp_well map received something of an upgrade when it was duplicated to provide another CTF map. Also, Valve added two community-created maps, cp_fastlane and ctf_turbine, to the official maps in a June 2008 update. In August, six new official maps (pl_badwater, arena_lumberyard, arena_ravine, arena_granary, arena_badlands, and arena_well) plus another community map, cp_steel, were added to the roster. In February 2009, three more community maps — cp_junction_final, cp_egypt, and arena_watchtower — were added to the official rotation. In May 2009's "Spy vs. Sniper Update" and August 2009's "classless update", new official and community maps as well as numerous gameplay changes were released. Among the new maps were plr_pipeline, arena_offblast, ctf_sawmill, cp_yukon_final, and three stages for the new King of the Hill game mode, KotH_viaduct, KotH_nucleus, and KotH_sawmill.
Most recently, in December 2009 the "WAR! Update" brought cp_gorge and ctf_doublecross.
In addition to Valve's maps, some servers host their own custom maps. If you join a server that has a custom map, you will automatically start downloading the map from their server. Even though these aren't Valve's maps, statistics are still kept on your matches. Custom maps range from "regular" maps that replicate gameplay from original maps to mods that convert the game itself.