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In early September, 1984, a woman stood in front of the Taco Time salsa bar in The Dalles, Ore., holding a small plastic bag filled with light brown liquid. Quickly and furtively, she squirted the solution into the salsa bucket and poured a little into the salad dressing. The largest bioterrorist attack in United States history had begun.

The origins of this brazen contamination go back to 1970, when Indian mystic Baghwan Shree Rajneesh (also known as Osho) began a new spiritual movement in Mumbai. Rajneeshee's teachings were an odd mix of capitalism, meditation, ethnic and dirty jokes, and open sexuality, earning him the title of "sex guru." By the early 1980s the movement had swelled to tens of thousands, with 30,000 people visiting Osho's commune in India each year.

But pressures from Indian authorities were mounting, and Rajneeshee wanted to establish a utopia. With the help of his right-hand woman Ma Anand Sheela, and her wealthy husband Marc Harris Silverman, the group purchased a 64,000-acre ranch in Oregon, renamed it Rajneeshpuram, and set about building their utopia.

Some 7,000 followers moved onto the ranch, where they all wore red, worked on the communal farms and helped build the community. Rajneeshpuram grew to include a 4,200-foot airstrip, a fire department, restaurants, a public transport system using buses, and a sewage reclamation plant. It even had its own zip code: 97741.

Naturally the influx of the red-clad cultists made the locals nervous. It didn't help that the Rajneeshees had set up a "Peace Force" that walked around the commune carrying Uzis and drove a Jeep with a .30-calibre machine gun mounted on it into town. Fights began to break out between the Rajneeshees and locals. A hunting magazine declared "an open season on the central eastern Rajneesh, known locally as the Red Rats or Red Vermin." The Rajneeshees meanwhile began to take over entire Oregon towns, including Antelope, Oregon, which they promptly renamed Rajneesh.

With tensions high, the Rajneeshees were denied permits to build their city on a mountain. This is when the fight got very dirty indeed. Led by Ma Anand Sheela, who called herself Queen and carried a 357 magnum, the Rajneeshees attempted to take over the Wasco county government. When bussing in 2000 homeless people to vote the Rajneeshee members into state government positions failed—the government wouldn't let them vote—a new plan was hatched.

Over the course of two months, the group contaminated 10 salad bars in the area with salmonella in an attempt to suppress the vote. Using a plastic bag filled with a brown liquid they nicknamed "salsa," the poured the salmonella filled slurry directly into salad dressings, splashed it on produce, put it in water, and generally got it everywhere they could. 751 people fell ill, and 45 were hospitalized with Salmonella poisoning. No one died, but had the Rajneeshees gone with their original plan of using Salmonella typhi, or typhoid fever, it surely would have resulted in numerous fatalities. Despite causing widespread sickness, the plot didn't work. Locals suspected it was an attack of some sort and turned out in force to vote against the Rajneeshee candidates. But there was no concrete proof of malicious poisoning.

The contamination was originally attributed to poor worker hygiene. It wasn't until one year later, when Osho himself had fled the commune and blamed Sheela and her "gang of fascists" for the attacks that the government investigated. What they found in the commune was a fully fledged bioterrorism lab containing salmonella cultures and literature on the manufacture and usage of explosives and military biowarfare. Also discovered was one of the largest illegal wire-tapping operations ever found, and an assassination plot on the life of Charles Turner, United States Attorney for the District of Oregon.

As Osho, Ma Anand Sheela, and the various top members fled the country, the Rajneeshpuram quickly collapsed. Ma Anand Sheela and her co-conspirators were eventually caught and sentenced. Sheela was sentenced to 20 years in prison but released after just two years. She now lives in Switzerland and claims all her actions were at the behest of Osho. Osho himself died in 1990 and claimed to his death that Sheela was behind it all. The Rajneeshee movement still exists today in small pockets around the world.

The attack on The Dalles Taco Time salsa bar and nine other restaurants remains the first, largest, and worst bioterrorism attack in the U.S.

Visit Atlas Obscura for more on the Rajneeshee bioterror attack.

For a further account of cult bioterror, read the story of how Japanese doomsday cult Aum Shinrikyo, famous for its 1995 sarin gas attacks on the Tokyo subway, established a secret test lab on a sheep farm in the Australian outback.

Visit Atlas Obscura for more on the Rajneeshee bioterror attack.