Twenty-fifth Amendment to the United States Constitution
In 1841, the ninth President, William Henry Harrison, became the first United States President to die in office.  Before this, Representative John Williams had suggested that the Vice President should become Acting President if the President died. Also, after Harrison died, his Cabinet had met and decided that Vice President John Tyler would become "Vice-President Acting President." However, Tyler did not like this idea.  He announced that he had become the President, and was not just doing the old President's job.  He refused to look at any papers that were addressed to him as "Acting President."