South Carolina seceeded on December 20, 1860 after Abraham Lincoln won the 1860 election. However Lincoln did not become president until sworn in on March 4, 1861; so James Buchanan was still president when South Carolina seceeded.
The US stands for United States. So, you will often see the American leader referred to as "the president of the United States." He is sometimes referred as the POTUS (President of the United States).
The executive leader of the United States is the President.
A current United States President no longer holds the title of a United States President when a new US President is elected.
Abraham Lincoln was elected US President at a time of great political turmoil. The nation was being torn apart over the issue of slavery. He prosecuted a war against the seceeded southern states, and managed to put back together and preserve the USA.
The vice-president of the United States is the president of the US senate.
The Vice-President of the United States is the President of the US
The President of the United States heads the executive branch of the US government.
None, to be a US president the United States must be your birthplace
A regular US Navy Admiral, who fought for the Union.
No US president existed in 1664. Neither did the United States itself.
The commander in chief of all military forces in the United States is the US president. Quite naturally this president would heed the advice of many military and political advisors. The US Civil War saw the US President Lincoln play a large role in the conduct of that war.