Final answer:
In 1800, Thomas Jefferson was elected president, marking a significant event known as the 'Revolution of 1800.' James Madison, although associated with the Jeffersonian era, was not elected until 1809, succeeding Jefferson. Therefore, the correct answer is Thomas Jefferson's election in 1800.
Step-by-step explanation:
In 1800, the event that took place was the historical presidential election where Thomas Jefferson defeated incumbent John Adams. This election is notable for the peaceful transfer of power from one political party to another, often referred to as the "Revolution of 1800". In this election, Jefferson tied with fellow Republican Aaron Burr in the Electoral College voting, but the House of Representatives decided in favor of Jefferson after Alexander Hamilton swayed some Federalist votes against Burr.
In comparison, James Madison was elected president, starting his first term in 1809, following the end of Thomas Jefferson's second term. The year 1800 did not include Madison's election but did mark the beginning of Jefferson's first term as president. James Madison was Jefferson's close confidant and succeeded him in the subsequent election, not the one in 1800.