How Hemp Built the Age of Sail
Every European warship from the 16th to the 19th century ran on hemp. The sails were hemp. The rigging was hemp. The caulking was hemp. When the British Empire ran low, it nearly lost the seas.
For roughly three hundred years, the most important strategic crop in the world was cannabis sativa.
Not for smoking. For sailing.
A typical 18th-century ship of the line carried somewhere between 60 and 120 tons of hemp in its sails, ropes, and rigging — more in some cases than the weight of its cannons. The fiber was uniquely suited to the work. It resisted saltwater rot better than flax or cotton. It held knots without slipping. It could be tarred for weatherproofing without losing its strength. There was no good substitute.
Every major naval power knew it. Every major naval power had a hemp problem.
The British Bottleneck
England, the dominant naval power for most of the period, did not grow enough hemp domestically to supply its fleet. It imported the bulk of its naval-grade fiber from Russia — specifically from the markets at Riga and St. Petersburg — for centuries. This dependency was a recognized strategic weakness. When relations with Russia soured, the Admiralty panicked.
In the early 1800s, during the Napoleonic Wars, Tsar Alexander I joined Napoleon's Continental System and cut off hemp exports to Britain. The British response was, by some accounts, one of the underappreciated drivers of the War of 1812: an attempt to secure alternative North American hemp supplies and lock down the trade.
The colonies had been planted with similar fears in mind. King James I issued an order in 1611 requiring every Virginia colonist to grow hemp. Massachusetts and Connecticut later passed laws making hemp cultivation mandatory. The legislation was not about getting people high. It was about supplying the king's navy.
What Hemp Actually Did
A first-rate ship of the line carried roughly 30 miles of rope. The mainmast required cordage three feet thick. The standing rigging — the lines that held the masts up — was hemp. The running rigging — the lines that controlled the sails — was hemp. The sails themselves were a tightly woven hemp canvas. (The word "canvas," for what it is worth, comes from "cannabis.")
Ropes wore out fast. A working ship rerigged itself constantly. The Royal Navy maintained a vast logistical apparatus — rope walks, hemp warehouses, dedicated procurement officers — to feed the demand. The dockyards at Portsmouth, Plymouth, and Chatham were essentially industrial hemp facilities.
When the steam engine and the steel hull arrived in the second half of the 19th century, the strategic calculus changed almost overnight. By 1900, hemp was no longer the indispensable fiber of empire. By 1937, the United States had effectively banned its cultivation under the Marihuana Tax Act, making no distinction between fiber hemp and the psychoactive variety.
What We Forgot
The cannabis plant is one of the oldest cultivated crops in human history. For most of that history, the use case was not the flower. It was the stalk. The fiber that made the rope that held up the mast that carried the sail that crossed the oceans was the same plant that, today, gets debated as a recreational substance.
The Royal Navy did not have an opinion about THC. It had an opinion about saltwater rot. And on that specific question, it knew exactly what it needed.