I don't really understand what is being asked here, mainly due to the quotes encircling the term 'scientific research' implying it is something that is not scientific, not research or probably not both. Also, do you mean scientific research that is aimed at cannabis in general or on its legalization (the latter is basically of little to no consequence, as ban on cannabis is purely malum prohibitum)? Because of ambiguity of this question, let me address it part by part.

First and foremost, there were no real attempts to 'legalize' cannabis before the end of the 'prohibition' (or more precisely, until 1933, when the Volstead Act and 18th Amendment were repealed) as the cultivation, possession and any use of the cannabis and its products were largely legal until Marijuana Tax Act of 1937, with some regulations being introduced since 1860 that roughly corresponds with Opium Wars and increased awareness regarding the effects of various narcotics.

Second, cannabis products were just another herbal remedy and have been used for medicinal purposes for millennia as well as mentioned in ancient, medieval and modern herbaries and medical texts. Both axial and side effects of the cannabis have been detailed already in the works of Galen and in modern times the medicinal properties were re-evaluated by medicinal research and included in various medical textbooks, e.g. 'Handbuch der Pharmakologie' by Alexander Tschirch, published in 1911.

In 18th and 19th century, the trend was continued and hemp extracts were offered in apothecaries, usually as the alcoholic tincture (macerate) of hemp seeds or buds. It should be noted that contrary to the Indian practices, where smoking of leaves was popular, medicinal use of cannabis in Europe focused on tinctures or decocts (boiled extracts) made of hemp seeds. In the early 20th century mass-produced cannabis-based products gained popularity over hand-made apothecary products. They were usually marketed as antispasmodic, analgesic and hypnotic drugs and produced by e.g. Bickford, Eli-Lilly, Schieffelin & Co., Merrell and Evans. They fell out of use after the anti-cannabis campaign and Act of 1937 heavily decreased the popularity of the drug.

The idea of 'medical marijuana' i.e. marijuana smoked for medicinal purposed was definitely not popular among the doctors of the era (much like today) because of the intrinsic problems related to dosage that is heavily influenced by patient's reaction to smoke inhalation (reactions being usually heavily adverse in non-smokers) and due to the aforementioned tradition of oral consumption of hemp extracts.