The story of Dun Morogh.
Dun Morogh is a land of snow-covered pine forests and frozen peaks in western Khaz Modan, home of the dwarves and the gnomes. The gnomes came first; the dwarves arrived some five hundred years later and carved the great city of Ironforge out of the region's tallest mountain. The two peoples became firm allies, and dwarven masons helped the gnomes build their own city, Gnomeregan, in the west. Together the dwarves drove the Frostmane trolls who once ruled these mountains into the high hills, and together both races fought for the Alliance in the Second War.
The gnomes have since lost their home. Troggs boiled up out of the earth beneath Gnomeregan, and, betrayed from within by Mekgineer Thermaplugg, the gnomes' leader, High Tinker Mekkatorque, flooded the city with toxic radiation to wipe the invaders out. It failed, and most of the gnomes died. The survivors fled to Ironforge, where they live as guests of the dwarves, while irradiated leper gnomes and troggs still roam the city's ruined approaches.
The rest of Dun Morogh is still dwarf country. New dwarves and gnomes begin in Coldridge Valley before heading to the village of Kharanos and its famous brewers, the Thunderbrews. The Barleybrews hunt for the perfect ale in Brewnall Village, troggs fight the miners at Gol'Bolar Quarry, and the Frostmane trolls and the wendigos of the high caves keep the snowy roads dangerous.
Written for this site from the game's lore. Further reading: Dun Morogh on Warcraft Wiki.

