I'm planning to start an Old School Campaign next week, for players who have mainly played D&D 3.0 and 3.5. I'd like them to play a real classic old school module. I have both B1 - In Search of the Unknown and B2 - The Keep on the Borderlands, which are extremely early published modules. Is there anything earlier than these, maybe something that was included with the White Box?
If you look at
It seems to be that Palace of the Vampire Queen was the first somehow published Adventure in 1976.
Edit: Here are some more details about it: It's the first D&D Module ever published, but not the first TSR one. There was also a scenario that was published earlier in the Blackmoor supplement.