How did John Quincy Adams become President in 1824?

Answer: It was the first election in which the winner did not achieve at least a plurality of the national popular vote. The Democratic-Republican Party had won six consecutive presidential elections and was the only national political party.

Explanation:

Andrew Jackson won a plurality of electoral votes in the election of 1824, but still lost to John Quincy Adams when the election was deferred to the House of Representatives (by the terms of the Twelfth Amendment to the United States Constitution, a presidential election in which no candidate wins a majority of the electoral vote is decided by the House of Representatives).

Answer: John Quincy Adams became President when the House of Representatives chose him to be so. It was the first election when the winner did not achieve at least the advantage of the national public vote.