The business is truly multinational, but the "spice" road begins in China. ABC News tracked the trail of the chemicals back to laboratories outside Shanghai.
An ABC News producer in Shanghai went undercover to meet with two factory representatives from Sciencya Laboratories at a park outside a downtown hotel, and was offered large quantities of the legal chemicals at $5800 a kilo with a speedy delivery time for her convenience.
"She said I should order about 10 kilos and arrival could happen through air mail in 4-7 days. And then she asked me to put them in my bag and not let people see them," said producer Rebecca Kanthor. The woman representing SciencYa also gave Kanthor samples of the chemicals.
Once manufacturers in the United States have bought the chemicals in bulk, mostly from China, they apply the chemicals to plant matter to create "spice" and other variants of "legal marijuana" or "herbal incense," then distribute their products either to wholesalers, directly to convenience stores, or to individuals who buy them on the internet.
ABC News found a wholesale operation in Denver that supplies a variety of products of all kinds to mom and pop shops in the area. An ABC News producer wearing a hidden camera recorded video of boxes of spice products in the back of the warehouse sold at bulk prices.
A representative of the warehouse said his company is in the process of phasing out spice products and that it only sells products with legal chemicals in them.
Christopher Van Winkle, who went to state prison in 2006 for manufacturing and delivering marijuana, makes and markets his own brand of herbal incense, "Magnum," and sells it on his website, TheChemicalBay.com.
He runs his operation out of apartment complex in a residential part of Bloomington, Illinois.
Van Winkle did not respond to an ABC News request for comment.
Van Winkle, like most other herbal incense manufacturers, labels his products as "not for human consumption," which exempts them from regulation by the Food and Drug Administration.
The laboratories in China also use language to avoid such regulation. The web site for a Shanghai pharmaceutical company, Chemchallenger, states "All products on this web site are only for research!" SciencYa Laboratories also says it sells only chemicals that have not been banned by U.S. law.