Canadian cannabis producers are rushing to enter the US market following the passage of the Farm Bill, which legalized hemp — a source of the popular ingredient cannabidiol, causing millennial investors to scoop up shares of these companies.

On Monday, Canopy Growth announced it has received a license from New York state to process hemp and that it intends to invest millions of dollars to build its first extraction and processing operation site outside Canada. Also on Monday, rival Aurora Cannabis told Business Insider it will unveil a plan to produce hemp-derived CBD for the US market in the next few months.

The financial opportunity could be enormous — Cowen analyst Vivien Azer says the US CBD market currently generates $418 million in sales and that's expected to climb to $1.6 billion by 2021.

And it seems investors on Robinhood— a free trading app popular among younger traders — were also seizing the opportunity. According to data tracked by Markets Insider, four of the five most-added stocks in the past week were Canadian marijuana companies.

• Aurora Cannabis: +29,368 shareholders
• Canopy Growth: +9,936 shareholders
• Cronos: +5,464 shareholders
• Tilray: +3,182 shareholders

Ford was the fourth most-added stock, with a net 5,389 Robinhood traders buying the stock in the past week.

Aurora Cannabis was the 3rd most-popular stock on the app in terms of the number of users who owned the stock, following Apple and General Electric. Cronos was the 7th, Canopy Growth 13th, and Tilray 45th.a