When business legend John Jacob Astor died in 1848, he was hailed as a titan of trade and praised as a sharp salesman with a taste for philanthropy. “There are few men whose biography would prove more instructive or more acceptable for the present age than the life of John Jacob Astor,” gushed one magazine in his obituary.

But today, one facet of the first multi-millionaire biography might seem to tarnish his shining legacy: his dabbling in smuggled opium. Astor’s enormous fortune was made in part by sneaking opium into China against imperial orders. The resulting riches made him one of the world’s most powerful merchants—and also helped create the world’s first widespread opioid epidemic.

Born in Germany, Astor’s enterprising spirit took him abroad when he was just 18. He ended up in the United States at a time when the country was in the midst of a new love affair with China.

As Astor began to sell furs in New York, he kept tabs on America’s new China trade. The country had a longstanding obsession with Chinese goods, especially tea that had fueled revolutionary sentiment against the United Kingdom. During British rule, American trade was under England’s thumb, and the East India Company had a monopoly on trade with China. The Revolutionary War changed that, and the new United States, now free of the monopoly, could trade freely with China. American ships began to sail directly to Canton, and the flow of commerce that followed made millionaires out of the intrepid men who plunged into the trade.

Astor began to import Chinese tea and silks—and to flirt with another way to get in on the trade boom.

“The China trade was an early engine of American investment,” notes Eric Jay Dolin for The Daily Beast. The merchants who became millionaires thanks to commerce with China also became philanthropists—but there was a downside. “These American fortunes, and all their good works…must be weighed against the damage that was done in acquiring them,” writes Dolin.

That damage took the form of drugs—namely, opium. Since there wasn’t much demand in China for western goods, England and the United States made up for it by providing something that was. They used the profits from opium to purchase tea, pottery and fabrics that they’d resell back home. This also allowed merchants to get around a big technical challenge: an international shortage of silver, the only currency the Chinese would take.

Opium was technically banned in China, but merchants like Astor found a way around the ban. Large ships containing gigantic hauls of opium met small vessels outside of legitimate ports and swiftly unloaded their illicit cargo. Bribery was common and officials who had taken bribes looked the other way instead of enforcing anti-opium laws.

Astor knew that British ships usually smuggled in premium opium from India, but he wanted to get a foothold in the opium trade. For his first salvo, he purchased 10 tons of Turkish opium in 1816. The quality wasn’t as high as Indian opium, but it was still in demand: dealers cut Indian opium with their Turkish supply. Astor shipped the opium to China in exchange for goods that he resold in the United States.

It isn’t clear how much opium Astor sold during his years as a drug smuggler, and the business was just a lucrative sideline to his even more profitable fur trade. But Astor is thought to have sold hundreds of thousands of pounds of opium between 1816 and 1825 when he stepped away from the China trade for good. According to historian John Kuo Wei Tchen, Astor even brought opium to New York, openly selling it and even advertising it in New York newspapers.

By selling opium, Astor was satisfying an international craving that would reach epidemic proportions during the 19th century. Opium use became rampant in China, where 3 million people smoked opium in the 1830s. By 1890, a full 10 percent of China’s population smoked opium. In a bid to curb opium use, imperial China banned producing or consuming the drug, even executing dealers and forcing users to wear heavy wooden collars and endure beatings.

Smugglers like Astor fed that demand without taking on too much risk; as Frederic Delano Grant, Jr. notes, American smugglers overlooked the consequences of the trade. “Perhaps the opium traders’ inability to see most Chinese as other than menials or curiosities helped them keep faceless the hundreds of thousands of Chinese who craved the drug they sold,” writes Grant.

Astor wasn’t the only American to make his fortune in part through opium smuggling: Warren Delano, Franklin Delano Roosevelt’s father, made millions engaging in what he called a “fair, honorable and legitimate” trade.

Opium smoking and injection of opium derivatives like morphine created hardcore drug users in England and the United States, but the main toll of opium use in the West was felt among casual users who started using opium under doctor’s orders. Opium use was socially acceptable and medically approved in some forms and could be found in patent medicines prescribed for everything from pain to depression.

This led to widespread addiction and became, in effect, America’s first opioid epidemic. In 1859, Harper’s Magazine wrote of “glassy eyes in Fifth Avenue drawing rooms and opera-stalls” and “permanently stupefied” babies—all people who took or were given opium in prescription or over-the-counter form. It would take until the late 19th century for American doctors to curb their prescriptions of opium derivatives to patients.

By then, opium abuse had devastated China and caused two wars. Astor, long since dead, had passed his fortune on to a family that became a Gilded Age fixture and dominated New York philanthropy and high society.

Astor’s reputation didn’t suffer from the trade—though it was illegal in China, Astor conducted his drug deals openly. But by participating in the opium trade in the early 1800s, he helped create a system that fueled addiction worldwide—and made millions while he was at it.