That's not entirely true. Historically, the US distinguished between European hemp (aka Cannabis Sativa), grown for its fibres and with a lower THC content, an

That's not entirely true. Historically, the US distinguished between European hemp (aka Cannabis Sativa), grown for its fibres and with a lower THC content, and Indian hemp (aka Cannabis Indica), which was sometimes grown for its fibres but had a higher THC content. Eg, the Internation Opium Convention of 1912 restricted exports of "Indian hemp" but not European hemp. Mind you, plenty of farmers did grow "Indian hemp" for fibres, including (somewhat amusingly) George Washington, who imported Indian hemp seeds for that purpose, and is on record as saying it was much more valuable for fibre production that "common hemp". Whether those were ever really different plants, or what exactly the THC levels of any of them would have been is not clear. :) But the distinction is one that was routinely made both by farmers and government.