Article Three of the United States Constitution
Before it won its independence in the American Revolutionary War, America was a colony of the British Empire.  The Founding Fathers wrote the Constitution just four years after the War ended.  They still remembered what the courts in the American colonies were like.  As Thomas Jefferson wrote in the Declaration of Independence, Britain's King George III "made judges dependent on his will alone, for the tenure of their offices, and the amount and payment of their salaries."