Bordeaux is classified in more detail than any other wine region in the world with its 57 appellations covered by six different classifications:
The 1855 Sauternes and Barsac Classification
The 2012 St Emilion Classification
The 1959 Graves Classification
The 1932 Cru Bourgeois Classification
The 2006 Médoc Crus Artisans Classification
Pomerol has never been classified, probably due to its relative anonymity before the 1960s. Ch. Pétrus is informally recognised as a First Growth in quality but has no legal right to that description on its label. Bordeaux was not the first wine region to be classified. As far back as the 14th century a list was made of Jurançon's finest vineyards while in 1644 the best wines of Franken in Germany were officially identified. However, there is no question that Bordeaux's classification system is the most important, well-known and influential example in existence. Its flagship is the 1855 Classification of the Médoc which saw the region's top 58 estates classified into 5 levels of Classed Growths.
Most of Bordeaux's classifications - notably those for the Médoc, Sauternes and Graves - have never been updated, despite various attempts to do so. That for St Emilion, however, is regularly reviewed; the latest classification took place in 2012. Status has always been important in Bordeaux and it is thus not entirely surprising that all attempted reclassifications are fraught with problems.
Today, from a consumer's view at least, other factors like the 100-point scoring system and reviews from prominent wine journalists like Robert Parker have arguably replaced the purpose of the age-old classification systems. This certainly explains why châteaux like Cru Bourgeois Sociando-Mallet and St Emilion's Ch. le Tertre Rôteboeuf have decided to opt out of the system. Such a scenario must surely make the late Baron Philippe de Rothschild turn in his grave. After all, Rothschild campaigned tirelessly for 50 years to upgrade Ch. Mouton Rothschild from a 2nd to a 1st Growth - representing the only alteration that has ever been made to the 1855 classification.
Nevertheless, being one of the 61 Classed Growths of 1855 or a St Emilion Premier Grand Cru Classé remains of considerable importance. And to be fair, all of the Bordeaux classifications remain broadly accurate. In some cases this is because they have been recently updated - like St Emilion and the Cru Bourgeois classification - and for others - like the Médoc, Graves and Sauternes - because they were pretty accurate in the first place, being largely based (albeit indirectly) on terroir.
Bordeaux's classifications have also performed a vital marketing service in highlighting and promoting the region's finest wines. With 10,000 châteaux and domaines farming 120,000ha of vineyards, they cover only a small proportion of the total number of Bordeaux's producers. But they have led to iconic wines like Mouton, Lafite and Margaux becoming synonymous with Bordeaux and thus providing a halo effect for the whole region. Contrast this to Germany which has no equivalent system and whose wines are synonymous with the famous but low quality Liebfraumlich, Blue Nun and Black Tower.