The Articles of Confederation was the first constitution of the United States of America and was in effect from 1781-1789.  There were eight individuals appointed by Congress for a one-year term in office, and each was referred to as “President of the United States in Congress Assembled.”  When John Hanson of Maryland was appointed in 1781, he was the first to serve the one-year term in office as specified in Article IX of the Articles of Confederation:

The United States in Congress assembled shall have authority… to appoint
such other committees and civil officers as may be necessary for managing the
general affairs of the United States under their direction—to appoint one of
their members to preside, provided that no person be allowed to serve
in the office of president more than one year in any term of three years;