Mercurius
Legend
It seems that every edition of D&D has had an iconic setting - a campaign world that highlights and exemplifies the specifics of the system, in a sense saying "This is what we had in mind." Yet instead of just one iconic setting, I would argue that most editions have two: a formative setting that outlines the general gist and atmosphere of that edition as a starting point, and a climactic setting that arises at the edition's peak and pushes the boundaries and explores the possibilities.
OD&D
Formative - Blackmoor.
Climactic - Greyhawk.
This is stretching it a bit as I'm not sure that you could say that Blackmoor was more formative to OD&D than Greyhawk, but afaik the first true RPG sessions were run by Dave Arneson in Blackmoor, although it was Greyhawk that really took off as the iconic early D&D setting and set the stage for 1E AD&D. Blackmoor instead went down the other road and became part of the BECMI line.
BECMI
Formative - The Known World (early Mystara).
Climactic - Mystara (the entire world).
I was never a big player of BECMI, so my understanding of Mystara is limited. But afaik, it was the only setting for BECMI and it started as a vague "Known World" implied setting, sort of like Nentir Vale for 4E, and developed over time into the world of Mystara, complete with the Hollow World, and incorporating Blackmoor in its past.
AD&D 1E
Formative - Greyhawk
Climactic - Dragonlance
This is pretty clear. Greyhawk was the dominant, early setting for AD&D, in many ways the Old School D&D setting in which most of the classic adventures are set. Things changed quite substantially in 1984 with the publication of Dragonlance, and the emphasis shifted from sandbox to metaplot. Dragonlance paved the way for all later campaign settings, especially the "flowering" of 2E.
AD&D 2E
Formative - Forgotten Realms
Climactic - Planescape
2E had many settings, although the most iconic was probably the Forgotten Realms, which technically started during the late years of 1E (the grey box was published 1987) but really exploded with 2E. Then you have highly experimental settings like Spelljammer, Dark Sun, Ravenloft, and Birthright, but the true climactic setting was Planescape, which could be seen as a cap-setting for all other settings.
D&D 3E
Formative - Forgotten Realms
Climactic - Eberron
While 3E used Greyhawk as its default setting, it was the Forgotten Realms that really formed its base. Eberron was the only truly official new setting and brought in elements newish to D&D such as steampunk.
D&D 4E
Formative - Nentir Vale
Climactic - ?
The closest thing to a formative setting is the Nentir Vale region, much in the same way that the Known World was formative to BECMI, as I said earlier. You could also say that the formative setting isn't Nentir Vale, but "points of light" as a theme.
Now it looks like WotC is going to develop the Nentir Vale, at least to some degree. But it remains to be seen what its climactic setting will be. I wouldn't call any of the three official settings released so far--the Forgotten Realms, Eberron, or Dark Sun--as either formative or climactic. They are all re-hashing what has come before and none either create the foundation of 4E or explore its possibilities.
Of course to get to a place where a truly climactic setting can arise from 4E, WotC first needs to establish a stronger foundational, formative base. So we will likely see further explication of the Nentir Vale and the new planes structure - with two Nentir Vale products and the Shadowfell box set already planned - but it will likely be 2012 or 2013 before we see what could be called the climactic setting of 4E.
OD&D
Formative - Blackmoor.
Climactic - Greyhawk.
This is stretching it a bit as I'm not sure that you could say that Blackmoor was more formative to OD&D than Greyhawk, but afaik the first true RPG sessions were run by Dave Arneson in Blackmoor, although it was Greyhawk that really took off as the iconic early D&D setting and set the stage for 1E AD&D. Blackmoor instead went down the other road and became part of the BECMI line.
BECMI
Formative - The Known World (early Mystara).
Climactic - Mystara (the entire world).
I was never a big player of BECMI, so my understanding of Mystara is limited. But afaik, it was the only setting for BECMI and it started as a vague "Known World" implied setting, sort of like Nentir Vale for 4E, and developed over time into the world of Mystara, complete with the Hollow World, and incorporating Blackmoor in its past.
AD&D 1E
Formative - Greyhawk
Climactic - Dragonlance
This is pretty clear. Greyhawk was the dominant, early setting for AD&D, in many ways the Old School D&D setting in which most of the classic adventures are set. Things changed quite substantially in 1984 with the publication of Dragonlance, and the emphasis shifted from sandbox to metaplot. Dragonlance paved the way for all later campaign settings, especially the "flowering" of 2E.
AD&D 2E
Formative - Forgotten Realms
Climactic - Planescape
2E had many settings, although the most iconic was probably the Forgotten Realms, which technically started during the late years of 1E (the grey box was published 1987) but really exploded with 2E. Then you have highly experimental settings like Spelljammer, Dark Sun, Ravenloft, and Birthright, but the true climactic setting was Planescape, which could be seen as a cap-setting for all other settings.
D&D 3E
Formative - Forgotten Realms
Climactic - Eberron
While 3E used Greyhawk as its default setting, it was the Forgotten Realms that really formed its base. Eberron was the only truly official new setting and brought in elements newish to D&D such as steampunk.
D&D 4E
Formative - Nentir Vale
Climactic - ?
The closest thing to a formative setting is the Nentir Vale region, much in the same way that the Known World was formative to BECMI, as I said earlier. You could also say that the formative setting isn't Nentir Vale, but "points of light" as a theme.
Now it looks like WotC is going to develop the Nentir Vale, at least to some degree. But it remains to be seen what its climactic setting will be. I wouldn't call any of the three official settings released so far--the Forgotten Realms, Eberron, or Dark Sun--as either formative or climactic. They are all re-hashing what has come before and none either create the foundation of 4E or explore its possibilities.
Of course to get to a place where a truly climactic setting can arise from 4E, WotC first needs to establish a stronger foundational, formative base. So we will likely see further explication of the Nentir Vale and the new planes structure - with two Nentir Vale products and the Shadowfell box set already planned - but it will likely be 2012 or 2013 before we see what could be called the climactic setting of 4E.