The map shows two flow-maps of the Atlantic trade in wool and cotton, three years apart. The time period covers the beginning of the American Civil War, which was sparked by the slavery policies of the Lincoln presidency. By January 1861, seven of the southern states had seceded to form the Confederacy. The war between the Confederacy and the states who remained in the Union lasted until 1865, and had a devastating effect on American exports. The seven separatist states are marked on both maps. The Confederacy attempted to use 'Cotton Diplomacy', cutting off the cotton supply to force European powers to intervene to save their domestic industries. In early 1861, the Union had not yet implemented its wartime blockade of the South, and cotton and wool could still be exported, but Britain and other major customers were worried about the stability of the American supply, investing heavily in production in South Asia.

A line graph in the upper right corner shows the yearly export amounts of wool and cotton for America (blue). There is a sharp drop in exports from 1860, when the issues provoking the Civil War came to prominence. Comparing the two maps gives an even clearer picture of the change; by 1861 the amount of cotton and wool imported into Britain from India (yellow) had almost tripled, whereas the amount imported from America (blue) had only risen by a paltry 16,000 tons. Britain was then re-exporting to other European countries (pink), at a rate three times higher than before the start of the Civil War.

Copies are held at ENPC: Fol 10975.

Charles Joseph Minard (1781-1870) was "a true pioneer in thematic cartography and in statistical graphics" (Friendly). After completing his studies at the École des Ponts et Chaussées, (the School of Bridges and Roads) he began work as a civil engineer. The beginning of his career coincided with the beginning of the Napoleonic Wars, and he headed a project to repair the wet dock at Flessingue after it was destroyed by the British. He was then posted to Antwerp to oversee a project there and was caught in the siege of Antwerp in 1814, an experience that affected him greatly. He was named Superintendent of his alma mater in 1830. Six years later, he became Inspector of the Corps of Bridges. In 1851, he took mandatory retirement, although still working for the school in an advisory capacity, and undertook private research. This is when his cartographical career began in earnest.

Minard's genius lay in his realisation that maps could provide visually clear renditions of complicated statistics. He wrote that the aim of his work was not to convey statistical results, but to show the relations between them, which would otherwise have to be worked out by the reader. He would often alter geographical reality on a map in order to make a diagram clearer, and so added the term 'approximative' to the title of his works to explain his decision. He was possibly the first to use the flow-map technique (his writing indicates that he believed he had invented it) and he was certainly the first to use pie charts on a map. His work was "a combination of cartographic ingenuity and concern with the graphic portrayal of statistical data that was almost unique during the central portion of the century" (Robinson).

The importance of Minard's work was quickly recognised by the French government. He was awarded the Legion d'Honneur, and throughout the 1850s all Ministers of Public Works in France had their portrait painted with a Minard chart in the background. In 1861, his work was presented to Napoleon III. Minard's maps were not widely known in his lifetime outside of the intelligentsia and upper levels of government, suggesting that he published them privately (Robinson).

Minard continued to write and create maps in retirement, until the onset of the Franco-Prussian War. In 1870 Minard heard that the Prussians were marching on Paris. Determined to avoid a siege like the one he had suffered under in Antwerp 56 years before, he left for Bordeaux. The journey was too much for him, and he died six weeks later.