7.  Franklin Pierce Age at inauguration: 48 years, 101 days In office: 1853–1857 Pierce was the 14th President and served one term. He was elected in 1852 and served 1853–1857. He authorized the Gadsden Purchase and the Kansas-Nebraska Act. Other highlights of his one term in office were few. He was not nominated for re-election. His party’s nominee, Democrat James Buchanan, won the Election of 1856.

6. Grover Cleveland Age at inauguration: 47 years, 351 days In office: 1885–1889 and 1893–1897 Cleveland is the only President to serve two nonconsecutive terms. He won the popular vote in three straight elections but won the Electoral College vote, and so the Presidency, only in 1884 and 1892. In his first term, he, a Democrat, utilized his veto power many times in disputes with the Republican-controlled Congress. During his second term, he sent federal troops to break up the Pullman Strike.

5. Barack Obama Age at inauguration: 47 years, 169 days In office: 2009–2017 The first African-American President, Obama entered office in 2009, just as the global financial crisis was accelerating. Not long after he was elected, he was awarded the Nobel Peace Prize. (Only three other Presidents, Theodore Roosevelt, Woodrow Wilson, and Jimmy Carter, have won that award.) During his first term in office, he signed into law the Affordable Care Act, a system of nationwide health care. He also ended the terrorist threat of Al-Qaeda leader Osama bin Laden, architect of the September 11, 2001, bombings of the World Trade Center and the Pentagon. Obama was re-elected.