The President of the United States of America is both the head of state, and the head of government for the United States of America, a political union on the North American continent on Earth. The office of president was estabished by the ratification of a constitution in 1787, and George Washington was the first person elected to that office.
In South Dakota, giant likenesses of five of the most memorable Presidents have been carved out of the granite in Mount Rushmore.
By the 23rd century, the office of President of the United States had become a largely ceremonial role, rather than a position with actual political power (TOS novel Spock's World). In 2375, following the Breen attack on San Francisco, the president joined Federation President Min Zife and the Prime Minister of United Earth in touring the city. (short story: "Eleven Hours Out")