Anybody know?
We chatted about this a couple of months ago.
Legislative, Executive, Judicial.
France had a legislature with three divisions; the nobility, the clergy, and the commoners. These were the three actual estates. When the media became an influential voice in political decisions it was refered to as the fourth estate.
God damnit! I was too late 
Little Nemo is correct, I am studying sociology at the moment and recently read up on the Enlightenment movement, I believe it was in their time that three state term originated.
The Enlightenment movement was very concerned with the power of the clergy over the third state, but less with their own aristocratic ways. So the second state became a model for what society should be and the middle class was slowly born as a powerful but educated intellectual ballas in society, sort of.
When the media arrived someone coined the phrase that they were now the fourth state, having influence over all the others, but I can’t for the life of me put a name or date to the phrase. It seems to be a very common phrase these days and probably hard to track. Any info would be appreciated.
— G. Raven
God damnit again! 
That was supposed to read ESTATE, not STATE.
Morrison’s Lament,
I believe that the concept of the three estates actually dates back to medieval times, not the Englightenment. For example, one of the posts in the link I provided indicates that the Estates General of France first met in 1302 and was then summoned from time to time until 1614. There was then a hiatus of 175 years, when the French kings ruled without calling the Estates General. When Louis XVI finally did, in 1789, it was one of the triggering events for the French Revolution.
Also in the link I provided, there are links indicating that Edmund Burke, M.P. is credited with coining the phrase “Fourth Estate.”
I stand corrected.
The term was used extensively in their writings and perhaps resurfaced as a popular concept at the time, but it almost certainly dates back further, as you pointed out.
— G. Raven