A Global Commodity History · c. 4000 BCE – today
How one molecule, pulled from half a dozen unrelated plants, travelled from a Peruvian midden to every pair of jeans on earth — through temples, guilds, sea routes, slave plantations, a peasant revolt and a German chemistry lab — told with open historical data and archival imagery.
Indigo deepens by repetition, not by a stronger bath: each dip-and-air cycle adds a layer.
Before the Story · One Molecule
Indigo is one molecule — indigotin — made by plants in at least four unrelated families: legumes in South Asia, Africa and the Americas, a cabbage relative in Europe, a knotweed in East Asia and an acanthus in the Himalaya. Cultures that never met found their own plant and arrived at the same chemistry.
“Blue is taken from the indigo plant, yet it is bluer than the plant.” 靑，取之於藍而靑於藍
Xunzi, “Encouraging Learning”, 3rd century BCE · Wikisource (Chinese)
Indigo is not in the leaf as a blue, and it does not dissolve in water. Every dyer on every continent solved the same two problems: make the blue, then make it soluble long enough to get it into a fibre.
Six Millennia · World Map
Scroll the timeline and the map follows the dye: a cotton scrap on the Peruvian coast, a recipe on a clay tablet, the Roman price of a luxury from India, a woad economy in medieval Europe, the sea route that broke it, the slave plantations of the Caribbean and Carolina, the Bengal ryots who refused to sow, the German laboratory that made them all obsolete, and the jeans that followed.
Diffusion & Time
Every mapped event on this site, placed by continent and date. The time axis is compressed — the first five thousand years share the left third — so that the last five centuries, when indigo became a world commodity, can be read at all.
Each dot is one cited event from the map above, coloured by era. The pattern is the argument: independent beginnings in the Americas, Africa, South Asia and the Mediterranean; a long medieval plateau; then five centuries in which the whole world is pulled into one trade, one industry and finally one factory product.
Dots are this site's mapped events, each carrying its own source (hover for it). The count is of cited turning points, not of every place indigo was ever used.
Ancient beginnings take millennia; the synthetic shock that ended natural indigo as a world crop took under two decades. Log scale.
Era boundaries are editorial (DERIVED): each opens at a cited event named in the tooltip.
Every source attached to a mapped event, counted by status. The ancient and medieval record leans on scholarship still being argued; the plantation and empire eras rest on customs ledgers and government returns.
Counts of source objects on this site's mapped events, not a measure of how much is known about each era.
Interactive · Year Scrubber
Drag the slider and the map fills in: each cited centre of indigo appears in the year its evidence begins. The cards give the trade figures for that year where a primary series exists, name the year each figure really comes from, and say so plainly when no series reaches that far back.
Saint-Domingue, South Carolina, Central America, Bengal and British India, each converted to tonnes from its source unit (DERIVED). The dashed line is the slider year.
Plantation Blue · 1650 – 1789
Between the 1650s and the 1790s most of Europe's indigo came from American plantations: French Saint-Domingue, Spanish Guatemala and San Salvador, British South Carolina and Georgia. These are their surviving records, each in the unit its source used.
Exports took off on a provincial bounty in 1747, Parliament's sixpence-a-pound bounty from 1749, and enslaved labour. The tallest bar, 1775, covers only the 6½ months to 24 February. Gaps are years with no figure in the series: 1767, and the Revolution — the bounty lapsed in 1777 and exports resumed only after 1783.
Saint-Domingue shipped more indigo to France than Carolina sent to Britain — over four million livres in 1771–72. Central American points mix harvests, exports and period averages (dashed line), so read them as orders of magnitude. French livres are converted to pounds at ×1.079.
Indigo works in the Saint-Domingue parish of L'Arcahaye: 186 in 1752, 23 by 1775, after irrigation turned the plain to sugar. Indigo was a crop for newcomers and smaller planters; sugar followed the capital. The 1789 figure is an estimate.
Empire Blue · 1790 – 1896
When the Atlantic supply failed, the East India Company rebuilt Indian indigo in Bengal; after Bengal's ryots revolted, the planters moved to Bihar. By the 1890s British India grew indigo on 1.7 million acres. Then the chemists arrived.
Two official series on one axis, both converted to tonnes: Bengal's production in factory maunds (1795–1831) and British India's exports in hundredweights (1876–1924). They measure different things — output and exports — but together they show the arc: about 5,300 t made in 1825–26, a record 9,517 t exported in 1895–96, and about 170 t by 1924–25.
From 1,705,977 acres in 1894–95 to 146,000 in 1914–15. The late spike is the First World War: with German supplies cut off the area rose to 765,000 acres in 1916–17, led by Madras rather than Bihar, then fell back to 107,000 by 1924–25. Official returns, fiscal years.
Synthetic Shock · 1897 – 1945
BASF's Indigo Pure went on sale on 10 July 1897. By 1905 Britain was spending more on synthetic than on natural indigo, and by 1914 natural manufacture had practically ceased everywhere except Bihar.
UK imports by value. Natural indigo fell from £1.53 million in 1896 to £137,000 in 1908. Synthetic imports, recorded from 1902, overtook it in 1905 — at a fraction of the old bill, because the price had collapsed too.
Index, 1897 = 100. India's average export value per hundredweight (to 1904–05) against BASF's price per kilogram (to 1914). By 1914 BASF's price was less than half its 1897 level. Both lines are computed from the cited figures (DERIVED).
The collapse was not only Indian. Tokushima grew about 15,000 ha of indigo in 1903; imported Indian and then synthetic indigo cut it to 7,542 ha by 1907, 502 by 1926 and 4 by 1965. A heritage craft has since held it near twenty.
Denim & Revival · 1946 – today
Almost all indigo now goes into one product. Published estimates of world output disagree by nearly half and no primary industry statistic exists; what has been measured carefully is the footprint of a single pair of jeans.
14,000 t consumed in 1995 by the reckoning of BASF's indigo chief, then estimates from 50,000 to 88,000 t a year in the 2010s and 2020s. Lighter bars are estimates. A 2024 market-research figure of about 97,000 t could not be traced to a readable source and is not shown.
Levi Strauss & Co.'s 2015 life-cycle assessment: 3,781 litres over a pair's life, two-thirds of it to grow the cotton; dyeing sits inside fabric production. UNEP puts an average pair at 3,000–4,000 litres and UN News has cited 7,500 — different boundaries, not comparable.
Where the Blue Went
Three moments, three models. A single Dutch fleet in 1631, itemised by origin; British India's exports in 1896–97, the last year before synthetic indigo, by province and market; and today's supply chain by origin and use. Band widths are pounds, hundredweights and percentages respectively; remainders and rounded shares are marked DERIVED.
The Human Cost
The trade's volumes were made by coerced hands. Guatemala's fermentation vats were deadly work; the plantations of Saint-Domingue and Carolina ran on enslaved Africans, bought in part with indigo-dyed Indian cloth; Bengal's ryots were bound by debt and Bihar's tenants by contract. Synthesis moved the costs rather than ending them.
“…it is in no instance the result of free agency, but that it is always compulsory.”
Ashley Eden, magistrate, on indigo cultivation in Bengal — evidence to the Indigo Commission, 1860 · Minutes of Evidence, Internet Archive
Open Archival Imagery
Fifty images from Tutankhamun's tomb to a Kano dye pit, every one public domain, CC0 or openly licensed: 17 public domain, 16 CC0, 15 CC BY-SA and 2 CC BY. They come from The Met, the Cleveland Museum of Art, Wellcome Collection and Wikimedia Commons, including uploads from the U.S. National Archives, the British Library, the Science History Institute, the Tropenmuseum and the African Studies Centre Leiden. Each card names its creator, license and record; the thumbnails are mirrored in the repository with their provenance, and each opens the full-size original.
Primary portals: The Met Open Access · Cleveland Museum of Art Open Access · Wellcome Collection · Wikimedia Commons · Indigo dye · U.S. National Archives catalog
Region Impact Matrix
Every centre of the trade, scored the way the Tampa study scored its districts: what the place did in the story, what it cost and whom, and where it stands now.
Source Audit
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About
An open-data history of one dye across six thousand years — where it came from, how it spread, what it cost, and who paid.
Indigo is the only colour that has been a world commodity for its whole history. This project follows one molecule from the oldest dated indigo-dyed cloth to the denim mill, with a world map, a set of charts, a year scrubber and a rights-cleared picture archive — and it shows its working for every number on the page.
It is a domain fork of Downtown Tampa: A Civic Development Autopsy, itself a fork of The 2026 Iran War: A Geoeconomic Autopsy: same architecture, same citation standard, a different subject — and a planet-sized study area. The site is static: no build step for the reader, no backend. Everything it knows lives in one cited data file, compiled from the research notes in the repository.
Every figure carries a source object naming the institution, the document, the date and a status, and most carry the exact sentence from the source that supports them. Nothing is presented as fact because it sounds right.
The Source Audit prints the live tally. Where sources disagree — the date of Maya Blue's first use, the depth of the blue layer in the Sacred Cenote, three incompatible figures for the water in a pair of jeans — the disagreement is printed, not averaged.
Several of indigo's best-known stories did not survive the research pass. The 1577 imperial ban on a "devil's dye" was aimed at a vitriol-based colour, not indigo; the German bans on indigo itself date from 1650 and 1654. No primary text was found for Henri IV's reported death penalty for using indigo; the documented French ban is from 1598. England's Elizabethan dye act of 1581 targeted logwood and names woad-and-indigo as lawful. Eliza Lucas did not create Carolina's industry single-handed. And "Japan Blue" as a nineteenth-century coinage could not be traced to a primary text. Each is noted where it would otherwise appear.
There is no trustworthy modern production statistic: published estimates of world synthetic indigo output range from 50,000 to 88,000 tonnes a year, and China's share can only be stated qualitatively. Britain's eighteenth-century imports by origin, the East India Company's early indigo volumes and an annual Guatemalan export series are named gaps. The research brief for closing them is in the repository.
The compiled dataset is released under CC BY 4.0. Embedded images are public domain, CC0 or openly licensed and credited on each card; anything whose reuse terms are unclear is linked rather than copied. See CONTENT_LICENSE.md for the full policy, and open an issue if you hold rights in something here.