The government's testimony before congress regarding the bill consisted largely of the testimony of the new director of the Federal Bureau of Narcotics, Harry J. Anslinger. Anslinger painted an ugly picture, reading aloud article after article about the horrors of Marijuana from Hearst's newspapers. Anslinger was well fitted for his new job, his previous one had been Assistant U.S. Commissioner for Prohibition. He had been hand-picked for his new position by his uncle Andrew Mellon, who also happened to be the owner and largest stockholder of the Mellon Bank in Pittsburgh. The same Mellon bank that also happened to be one of only two bankers for (drum roll please) the DuPont Company.
So, here the DuPont Companies connection to the proceedings becomes clear, but what was their interest in outlawing marijuana? In the beginning of the 1930's machinery to effectively and affordably strip hemp fiber and conserve it's high-cellulose pulp had just become readily available. In 1937, the DuPont Company had just patented process for making plastics from coal and oil, and a new process for making paper from wood pulp.
Plastic and paper made from hemp oil and pulp were the main competitors for DuPont's new synthetic based products. And competition they were indeed, not only was hemp a renewable resource, it was one of the heartiest, fastest growing plants on the planet! Even though DuPont's new synthetic products weren't readily accepted, they strongly urged investment, anticipating openly that government influence would play a large role in forcing their acceptance. And indeed, with the passing of the Marijuana Tax Bill of 1937, their largest competitor was suddenly outlawed and business exploded.
Anslinger's was not the only voice heard by congress on the bill. A few opponents were heard from in the proceedings. Dr. William G. Woodward spoke against the bill on behalf of the American Medical Association, stating that the entire case being against marijuana was based solely on tabloid sensationalism and that the AMA would have come out against the bill sooner had they known that the plant cannabis and the new drug marijuana were one and the same. However, when the bill came to the floor for a vote and the question was asked whether the AMA had been consulted, a representative of the Ways and Means Committee replied that they had, and a "Dr. Wharton" and the AMA were "in complete agreement." And with that lie and Anslinger's testimony that "Marijuana is the most violence causing drug in the history of mankind," the vote went to the floor and marijuana was outlawed.