These RPG supplements are set in D&D's first setting Mystara and begin in the year 1010 AC. The following books advance the year by one.
The Known World later became known as Mystara, and it's Mystara that's generally counted as the first official D&D campaign setting.
The Endless Stair is Ed Greenwood's first D&D book, and Greenwood created the Forgotten Realms.
Wizards of the Coast are taking back control of D&D in some countries after settling a legal row. Luke Crane's The Burning Wheel is Roll20's quickest growing system, and the inhospitable setting round table is coming. It's an RPG news summary from Geek Native.
The Krynn map covers the continent of Ansalon, with locations like elven-stronghold of Silvanesti, high plains of Palanthus, Sancrist Isle and the realms of the minotaurs.
The scan of TSR's World of Mystara D&D expansion Wrath of the Immortals is currently free to download from DriveThruRPG.