The Castries papers represents only a small portion of the original "archives" of the Maréchal. The core of the Castries Papers includes four major areas of interest:
1. The civil and military administration of French Caribbean colonies;
2. French participation in the American Revolution;
3. The 1784 trial to fix blame for the devastating defeat of the French Navy and the capture of Admiral de Grasse at the Battle of Saints Passage, 1782, and;
4. Royalist conspiracies against the French Republic during the 1790s.
The materials relating to French Caribbean colonies were collected by Castries in his capacity as Ministre de la Marine, a position that gave him some oversight of colonial affairs. Though undated, many of these documents appear to have been prepared in about 1783, and are perhaps related to negotiations at the Treaty of Paris or to the immediate outcome of that treaty. These documents include detailed descriptions of the French colonies in the Isles du Vent and Isles sous le Vent, with notes on administration, police, religious advancement, agriculture, trade, and defense.
Among the items from the period of the American revolution is an important document titled "Memoire en forme de Plan de la Campagne en Amerique dans l'année 1783 redigée par la Compte d'Estaing..." in which the author lays out a plan for global imperial conquest, beginning with the defeat of the British in North America. Also of great interest is the "Order à prendre du Roi, relativement à l'amérique Septentrionale," which contains an analysis of French military strategy in the Americas following Yorktown. A "Projet d'Arrêt du Conseil" of January, 1782, relates to reparations to the residents of Saint Eustatius for depredations committed there during its capture by British forces. Also present is the 1782 appointment of François Barbé de Marbois as consul in the United States.
The de Grasse trial materials contain an extensive body of records of the Conseil de Guerre Extraordinaire held at L'Orient, France, in 1784. These include a minute-by-minute reconstruction of the action at the Battle of Saints Passage (including manuscript maps, housed in the Map Division), interviews with French naval officers, manuscript and printed version of the findings of the Conseil with judgments against the naval officers (most were acquitted of any misconduct), and defenses written by the baron d'Arros d'Argelos and Pontèves-Gien to justify their conduct. All together, these comprise a thorough, though not quite complete documentation of the official inquiry into a major French naval defeat.
The 14 items relating to counterrevolutionary activity in the 1790s present a somewhat less complete picture than that for the de Grasse trial, but serve to indicate the breadth and depth of Castries' involvement in Royalist circles. These include letters from Royalists seeking assistance, documents outlining plans for a proposed invasion of the west coast of France, discussions of the possibility of Royalist forces capturing the colony of Saint Domingue and reestablishing it as a monarchy under Louis XVIII, and analyses of the potential for support among other European powers. Perhaps the most intriguing item in this part of the collection is a lengthy report from a British spy containing information on influential members of the French Directory with notes on whether they can be made useful to the Royalist cause.
The Castries papers are arranged chronologically. Eight maps entered as evidence at the Conseil de Guerre held at L'Orient have been transferred to the Maps Division.