Gallatin was born in Geneva in present-day Switzerland and spoke French as a first language. He immigrated to the United States in the 1780s, settling in western Pennsylvania. He served as a delegate to the 1789 Pennsylvania Constitutional Convention and won election to the Pennsylvania General Assembly. An opponent of Alexander Hamilton's economic policies, Gallatin was elected to the United States Senate in 1793. However, he was removed from office on a party-line vote after a protest raised by his opponents suggested he did not meet the required nine years of citizenship. Returning to Pennsylvania, Gallatin helped calm many angry farmers during the Whiskey Rebellion.