Berthier's maps, numbering 111, are the most notable feature of the collection. They do not comprise an atlas or a series of separate items, but, rather, they are the consecutive record of that important and historic Revolutionary War military event, the overland march of the French Army under Rochambeau (joined by American forces at Philipsburg) from Newport to Yorktown during the summer and early autumn of 1781, and the return march of the French Army from Virginia to Boston the following year, July - December 1782. These were executed, presumably soon after the event, from information and sketches made on the spot while Berthier was accompanying Rochambeau's Army in America. The maps fall into two interrelated series: the first showing the French Army's camp sites on the southward march from Newport, Rhode Island, to Yorktown, Virginia, in 1781, and on the return march northward in the summer and autumn of 1782; the second showing the "itineraries" or daily marches of the Army (from Newport as far as Elkton, Maryland, in 1781; the daily marches for the 1782 northward journey are lacking among the Princeton papers.) Another set of Berthier's maps is preserved among the Rochambeau Papers in the Library of Congress; this set, although duplicating in part the Princeton set, is apparently less complete

Although Berthier's maps are the most spectacular part of these papers at Princeton, they cannot be fully appreciated without the accompanying textual material of his journal (1780-1783), which provides a detailed description and explanation of the routes covered by the maps. In addition, there are related manuscripts and documents, including a letter (1785) from Rochambeau, notes on the history of Virginia, and Berthier's journal of his later visit to Prussia (1783).