His full name is James Knox Polk, and he is known for being the 11th President of the United States. He born back in the 18th century (in the year 1795), which is why there aren't a lot of photographs available from when he first started in politics. Before becoming president, he worked as Speaker of the House of Representatives.
After his tenure as Speaker of the House of Representatives, he became Governor of the state of Tennessee (from 1839 to 1841). He was a protégé of Andrew Jackson, which is why the public liked him so much. He was a member of the Democratic Party, just like his mentor, Andrew Jackson. During Polk's presidency, the US expanded its territories due to the victories over Mexico in the Mexican-American war.