OK, this one will be long. First, the monuments. France has a truckload (Wikipedia in French lists 80 of them, while recognizing not being exhaustive) of "well" (we will come to it) preserved castles and palaces in the Loire valley. This location puts them at a great level of security from outside threats, dodging all the fights in the War of the Spanish Succession (which were mostly in the Spanish Netherlands, Bavaria/savoy and Spain) and the Napoleonic Wars, as well as the World Wars. This means they are mostly affected by the internal strives, which, during this period, amount to two big phases : the 8 French Wars of Religion (1560 - 1598) and the French Revolution + First French Empire, where the anti-nobility strife leads to vandalism, requisition and sales to investors who will destroy parts of some castles.

So, the Wars of Religion. They start in 1562 and seem to dodge the main royal castles on the Loire, except Angers, which was ordered to be destroyed to not be captured by the huguenots. The demolition was never completed, as the hostilities ended in 1598. It seems to be the only attempt to maim a main royal castle in the period. But after the Renaissance, a good chunk are not properly maintained and are described to start falling in ruins before the Revolution, eg Angers, Blois.

The French Revolution is the start of a campaign of vandalism in all the castles nationwide. Furniture is stolen, destroyed, the royal castles and palaces are taken as public monuments, converted (Versailles was to become a museum and was especially protected, a good part of the others is converted to military bases, as Tours which retains only 2 towers of the original building, and the rest was only rediscovered in the 70s, or Saumur, Loches, Angers becoming prisons) or abandoned (Langeais). Chenonceau was also threatened of requisition and subsequent demolition but was saved by the fact it was a private property (fun fact : it belonged to the great-grandmother of George Sand). The furniture and paintings were stolen and destroyed though. Blois and Chambord narrowly escape demolition, but not Amboise, which lost 2/3 of its area during the Empire.

Those palaces are restored in a first wave during the Restoration and July Monarchy, and this is the moment where I talk about the maintenance procedure in France. The Revolution created the idea of historical monuments and the idea of keeping buildings is taken into account. A Museum of French monuments is opened in 1795 but closed at the Restoration. The first funds actively created by the French government to restore historic monuments is created in 1819, with 80 000 francs allocated between around 15 monuments. The main step up comes in 1840, when Louis Philippe creates the denomination Monument Historique, protectig 934 monuments, including Amboise, Chambord, Blois, Chenonceau and around 80 objects, like the Bayeux tapestry. The number of protected items increased since and is now at around 45 000 buildings.

The Monument Historique label covers two distinct levels : the "inscription" protects monuments with regional importance and the "classement" protects nationally and is given by the ministry of Culture. The repartition is, as of 2008, 14 000 monuments "classés" and 3 0000 "inscribed". This labels comes with some restrictions to the owner : all work done must recieve approbation from the prefect and the monument cannot be ceded without ministerial approval (for classed monuments). Furthermore, the nearby zone cannot be built on recklessly. The State finances a good chunk of all work, either though tax rebaits or direct aids