Final answer:
At the 1896 DNC, William Jennings Bryan used the phrase 'You shall not crucify mankind upon a cross of gold' to argue against the gold standard and advocate for the adoption of a bimetallic standard using both gold and silver.
Step-by-step explanation:
At the 1896 Democratic National Convention (DNC), William Jennings Bryan delivered a powerful and influential speech against the gold standard, which was a hotly debated economic policy at the time. The key phrase you are asking about is from this speech, in which Bryan declared, "You shall not crucify mankind upon a cross of gold." This statement was a dramatic part of his argument that the monetary policy should not unfairly burden the working class by adhering to a restrictive gold standard.
Bryan's speech was a rallying cry for the use of silver in addition to gold as a foundation for U.S. currency—a concept known as the bimetallic standard. He spoke passionately in favor of economic policies that would potentially benefit the common people, particularly the struggling farmers and industrial workers of the time. His fervent advocacy for free silver made him a champion of Populist causes and earned him the Democratic presidential nomination.