The Eastern Kingdoms
Alterac Mountains: The is the location of the old city of Alterac. Although Alterac was a human city, its leaders sided with the orcs instead of the Alliance in the Second War against the Horde. In return, the Alliance executed the leaders and burned the city, proving once again that it's not as simple as Alliance = good and Horde = bad. Yetis and ogres now infest the ruined city, and some of the old denizens of Alterac -- now a criminal organization named the Syndicate -- have set up shop in the surrounding hills. The mountains are also the home of the wizard city of Dalaran, which was destroyed by the Burning Legion and is now being rebuilt in a magical bubble.
Arathi Highlands: The Arathi Highlands were the home of the first great human state, the Empire of Arathor. Eventually, the Empire collapsed and its capital city, Strom, was left to a group of guardsmen who renamed it Stromgarde and turned it into a fortress. Arathi was overrun by the Horde in the Second War, but the guardsmen managed to rebuild Stromgarde and its sister village, Hammerfall, which was turned into an orc internment camp. The villages got destroyed AGAIN in the Third War against the Burning Legion, and the survivors gave up and created a small Alliance camp at Refuge Pointe. Today, Stromgarde is divided between humans, ogres and the criminal Syndicate, while Hammerfall is a Horde base camp. There's also a small cove with pirates in the south, which few ever see because it's very hard to get to.
Badlands: The Badlands are a bleak wasteland without much history. They've been inhabited by Horde forces fighting for a tactical outpost near the heart of the Alliance cities. The dungeon Uldaman, in the north, is an ancient Titan fortress that is now full of troggs and dwarves.
Blackrock Mountain: My burning hatred for Blackrock Mountain cannot be contained! This was the center of the pre-Burning Crusade universe for many guilds, as it contained the instances Blackrock Spire, Blackrock Depths, Molten Core and Blackwing Lair. In the base of the mountain, the elemental god Ragnaros was summoned by the Dark Iron dwarves, destroying the surrounding areas. At the top, Nefarian, the head of the Black Dragonflight, works with the Blackrock Orcs to fight off the dwarves and Ragnaros. Blackrock Mountain was the site of a major battle during the Second War, where Orgrim Doomhammer slew the Alliance leader Anduin Lothar.
Blasted Lands: The Blasted Lands used to be a swampy area called the Black Morass, until Medivh got the great idea to open a portal between Azeroth and Draenor. The resulting magical explosion destroyed all life in the area. Now only Kirin Tor mages watch over the area from Nethergarde Keep -- and of course, there's the now reopened Dark Portal for anyone who has the guts.
Burning Steppes: This zone used to be the home of the Dark Iron dwarves and their city, Thaurissan. Thaurissan was destroyed by the summoning of Ragnaros, leaving the area a dragon, orc and dark dwarf-infested wasteland. A statue of Anduin Lothar, who was killed in Blackrock Mountain, marks the middle of the zone. A demonic altar in the northwest was used by the orc Gul'dan to create ogre magi.
Deadwind Pass: The pass primarily serves as the gateway between the Swamp of Sorrows and Duskwood. The lower part of the area is dominated by Medivh's old tower, Karazhan, and is haunted by many high-level ghosts. Something -- possibly Medivh's dormant magic or the mysterious Dark Riders of Duskwood -- killed the villagers around Karazhan.
Dun Morogh and Ironforge: The snowy mountains of Dun Morogh are the home of the dwarves and gnomes. The cities of Ironforge and Gnomeregan lived in peace and joined the Alliance together in the Second War. Gnomeregan was later invaded by troggs and then turned radioactive by a gnomish mistake, so the gnomes moved into Ironforge. Neither Ironforge nor Gnomeregan ever fell to Horde invaders, although a lot of Horde seem to spend time attempting to invade Ironforge through the Deeprun Tram (between Stormwind and Ironforge.)
Duskwood: Duskwood is a gloomy place with a ton of cemeteries. The zone is shrouded in darkness, except for a giant volcanic crater in the middle that is full of a. life and b. dragons because of a link to the Emerald Dream. In the past, the towns of Darkshire and Raven Hill were normal, peaceful places. But then a night elf (it's always a night elf) came to town with an object called the Scythe of Elune and lost it in a mine. The Scythe began to curse the area, turning the skies dark and summoning worgen all around. The most important thing to know about Duskwood is that there are two wandering elites, Stitches and Mor'Ladim, that would like very much to kill you.
Eastern Plaguelands: The Eastern Plaguelands were hit pretty heavily by the undead plague. Everything that roams here is evil, cursed, or something else bad. Restless ghosts roam the area, many of them refugees from the Battle of Darrowshire (undead 1, living 0.) The city of Stratholme, in the north, was where Arthas first broke from Uther's teachings by killing all the plague-infested citizens, and is where Balnazzar commands the Scarlet Crusade in secret today. The city of Tyr's Hand is also full of Scarlet Crusade and your friendly neighborhood gold farmers. Naxxramas, floating above the Eastern Plaguelands, is the citadel of Kel'Thuzad and the source of the local Scourge.
Elwynn Forest and Stormwind: Elwynn Forest is a quiet, pastoral area, home to many farmers, bandits, and a crazy cat lady. The forest and Stormwind both came under siege in the First War between the Horde and Alliance, but the wounds of battle have mostly healed. Now, the forest's main enemies are the Defias Brotherhood, a group of masons and architects that helped rebuild Stormwind after the war but got kicked out of the kingdom instead of paid. Frankly, I think the Brotherhood has a good point here and should be given back wages. The human capital of Stormwind features statues of the great heroes of the Alliance Expedition and a nifty subway to Ironforge -- however, all is not well in the city. The dragon Onyxia helps rule Stormwind disguised as Katrana Prestor, and most of the city's ruling nobility are corrupt and frivolous.
Eversong Woods and Silvermoon City: This is the heart of Quel'Thalas, the home of the High Elves. Their beautiful city, Silvermoon, lies half in ruins because of the incursion of Arthas and the undead Scourge. The Dead Scar runs through the land as a testament to the invasion, while four runestones in the area protect Eversong from suffering the same fate as the Plaguelands. There's also a shrine to the first Sunstrider king, Dath'Remar, on the Blood Elf starting island.
Ghostlands: The Ghostlands (previously known as the Blackened Woods) were where the High Elves first landed before founding Quel'Thalas. Today, the Forsaken and the Blood Elves work together to fight the Scourge. Windrunner Spire, in the west, is the home of the Windrunner sisters (Allessia, Sylvanas, and Vereesa.) The troll stronghold and future dungeon Zul'Aman lies in the south, along with the citadel Deatholme. Dar'Kahn Drathir, the traitor that let Arthas into Quel'Thalas, ruled this citadel until I killed him.
Hillsbrad Foothills: This is a good place for lower level players who enjoy being ganked for hours on end. The Horde and Alliance cities of Tarren Mill and Southshore are both rich in history and really close to each other. Areas of interest include Tarren Mill, which was wiped out by the Scourge and turned into a Forsaken village; Durnholde Keep, where Thrall was raised and later escaped from; and Ravenholdt Manor, the home of a secret rogue society that may have been founded by the assassin Garona Halforcen.
Hinterlands: The Hinterlands, formerly known as Northeron, has a lot of troll villages. Good thing no one cares about trolls! But seriously, this is the home of the forest troll clans Vilebranch, Witherbark and Revantusk. The trolls aided the Horde in the Second War against the alliance, but returned to the Hinterlands after the Horde's defeat. After the Third War, when the Horde established itself in Kalimdor, they offered to help the troll clans rebuild their villages. Only the Revantusk agreed, and now live in a prosperous fishing village on the ocean and are considered part of the Horde. This wooded area is also the home of the Wildhammer dwarf clan, whose gryphon riders were invaluable to the Alliance in the wars against the Horde and the Burning Legion. There's a portal to the Emerald Dream in the north of the zone, but entrance is not recommended due to the big angry dragon in front of it.
Loch Modan: Loch Modan is a big lake with some dwarf cities around it. Aside from some minor Horde v. Alliance battles, not much of historical significance has happened here. Nice dam at the top, though!
Redridge Mountains: Redridge is a pretty but somewhat boring area east of Elwynn Forest. The human city of Lakeshore is mostly peaceful, but to the north, the Blackrock orc clan infests the hills, and an evil mage dwells in the Tower of Ilgalar in the east.
Searing Gorge: Searing Gorge is the major base of the Dark Iron dwarves, who have undermined most of the area. Like the Burning Steppes, the Searing Gorge was shattered by the summoning of Ragnaros, and is mainly known as a gate to Blackrock Mountain. Anyone who's made the death run between Thorium Point and Blackrock Mountain over a hundred times gets a cookie.
Silverpine Forest: Much like Tirasfal Glades, Silverpine Forest was a peaceful area -- watched over by three kingdoms -- until it got nuked by the plague of undeath. With Lordaeron destroyed, Dalaran rebuilding, and Gilneas walled off from the rest of the world, Silverpine was turned into a Forsaken area. It was also infested with werewolves who have a strong tendency to come out of nowhere and one-shot unsuspecting players. The Greymane Wall, in the south, protects the isolated kingdom of Gilneas.
Stranglethorn Vale: Stranglethorn Vale is one of the biggest zones in WoW, and takes up 15 levels of painful questing. It was originally settled by the trolls of the Gurubashi empire, who have since been driven back into isolated ruins and the temple of Zul'Gurub. The goblin trade princes have taken up much of the remaining space, establishing the neutral city of Booty Bay and pretty much demolishing the area. The Horde outpost of Grom'Gol is named for Grom Hellscream.
Swamp of Sorrows: The Swamp of Sorrows used to feature the only group of Broken Draenei in Azeroth. But since the Draenei's magic spaceship or whatever crashed into Kalimdor, they're now just sad evolutionary freaks, like chimpanzees dressed in tuxedos. The Green Dragonflight guards an ancient troll temple in the center of the swamp, and the Horde has built the large outpost of Stonard here.
Tirisfal Glades and Undercity: A lot of history happened here. This was the hub of the kingdom of Lordaeron, and the ruins over Undercity marks where Arthas killed his father. In fact, if you stand in the throne room and turn the sound up, you can hear the nefarious deed. The whole Undercity is where Arthas planned to rule Lordaeron, but Sylvanas and the Forsaken took it over after he got driven back to Northrend. The northern city of Brill was one of the first cities to be infected by Kel'Thuzad's plague of undeath, and is now a Forsaken stronghold.
Western Plaguelands: As you might guess, this area was ravaged by the plague of undeath. The cities Hearthglen and Andorhal, which used to be regular towns, were turned into a Scarlet Crusade stronghold and an undead-infested ruin, respectively. Andorhal was the center for grain distribution in Lordaeron, and was thus the place where Kel'Thuzad poisoned the grain to turn everyone into zombies. In the far south of the zone lies the tomb of Uther the Lightbringer, the first paladin, who was killed by Arthas. Horde members get a quest to defile this tomb, and then Uther's ghost appears and is disappointed in you, which made me feel really bad (see top photo.) Kel'Thuzad's Cult of the Damned runs the evil wizard Hogwarts, Scholomance, in the southeast.
Westfall: These plains are the Nebraska of WoW. A mysterious drought has given the land over to predators and gnolls, and members of the Defias Brotherhood have set up bases at the area farms. The low-level dungeon of the Deadmines is in the south, and the Defias commander Edwin Van Cleef is building a ship to destroy Stormwind there. The Deadmines is still the coolest instance in WoW.
Wetlands: The Wetlands are a large, Alliance-dominated area bridging the gap between human Lordaeron and dwarf Khaz Modan. The large port town of Menethil Harbor, named after King Terenas Menethil II, lies in the west. The Thandol Span bridge -- a giant dwarven engineering project -- connects Arathi Highlands with Wetlands, but it has been damaged by repeated wars. The ancient dwarven city of Grim Batol covers most of the eastern Wetlands. This was the ancestral home of the Wildhammer Clan, but after it was invaded by Dark Iron dwarves and Dragonmaw orcs, they found it unsuitable and moved to Aerie Peak. Grim Batol is where the red dragonflight queen Alexstrasza is rumored to hold Deathwing captive -- a.k.a., you have been warned.