Over 1,000 economists begged Hoover not to sign this tariff. He signed it anyway.

The Smoot–Hawley Tariff Act of 1930 raised US duties on over 20,000 imported goods, meant to protect American jobs as the Great Depression began. Trading partners retaliated with tariffs of their own, and global trade collapsed by roughly two-thirds over the next few years, widely blamed for deepening the Depression.

— Wikipedia contributors, Smoot–Hawley Tariff Act — Signed 17 June 1930