WotC's D&D Alumni series has a new article called An Elementary Look at the Planes. The article takes a look at the history of the elemental planes from the Great Wheel article of Dragon Magazine #8 (July 1977), through various sourcebooks and adventures, their codification in Manual of the Planes in 1987, right up to the Elemental Chaos of D&D 4E and the return to a variation of the Great Wheel in 5E.
Find the article here.
Find the article here.