La carte de France de Cassini. Une encyclopédie du territoire

A cartographic masterpiece of the eighteenth century, the Cassini map of France is the first map of France surveyed geometrically across an entire country. An emblematic historical document made up of 181 sheets, it is also a monumental work of art eleven metres wide and twelve metres high. Drawing in particular on a major transfer by the IGN to the Archives nationales, the exhibition traces the history of the map in a new light.

In 2021 and 2025, the National Institute of Geographic and Forest Information (IGN) transferred to the Archives nationales the archive collection relating to the Académie's map of France, better known as the Cassini map of France.

This remarkable collection consists of calculations, writings, minutes, but also copper plates and original prints documenting the making and life of this map between 1750 and the 1950s.

A collection of exceptional character which today allows us to reveal little-known aspects of a work of universal significance: a work conceived by four generations of astronomers and cartographers, the Cassinis.

The art of science: the first map surveyed 'geometrically' across an entire country, the kingdom of France, at the time the most powerful and most populous in Europe, is admirable in more than one respect.

It is, first, the product of a continuous state will which, with Louis XIV and Colbert, Louis XV and then Bonaparte, decided on and perpetuated the project, even though, from 1756 to 1793, a private company partly financed it.

It involves the use of innovative scientific techniques, for method and instruments, which tie it to the creation of the Académie des sciences in 1666 and the Paris Observatory in 1667.

It arises from the perseverance of scholars who carried it out until 1815, alongside the dynasty of the four Cassinis from 1669 to 1793.

It results from fieldwork followed by restitution through engraving, at once meticulous, standardised, sometimes difficult, and very long-term, from the surveys of Abbé Picard in 1668 to the last verified surveys in 1790.

It is, finally, beyond all norms in its final deployment: in space, of course, since the 181 assembled sheets measure over twelve metres high by eleven wide; but also in time, for from the first works in 1668 to the final use of the plates in the 20th century, almost three centuries elapse!