John Q. Adams character jug produced by Sebastian Originals of Encino, California, circa 1973. John Quincy Adams (1767-1848) was an American statesman, politician, diplomat, lawyer, and diarist who served as the sixth president of the United States, from 1825 to 1829. He previously served as the eighth United States secretary of state from 1817 to 1825. During his long diplomatic and political career, Adams served as an ambassador and also as a member of the United States Congress representing Massachusetts in both chambers. Adams is widely regarded as one of the most effective diplomats and secretaries of state in American history, but scholars generally rank him as an average president.