President pro tempore of the United States Senate: Timeline

1793   John Langdon becomes President Pro Tempore of the United States Senate until March 3

1799   Federalist James Ross becomes President Pro Tempore of the United States Senate.

1849   Zachary Taylor Zachary Taylor

Zachary Taylor was an American military leader [i] and the twelfth President of the United States [i] ... 

 refuses to be sworn in office on a Sabbath Sabbath

In the Bible [i], the Sabbath is a weekly religious day of rest as ordained by one of the Ten Commandments [i] ... 

 (Sunday). Consequently the office of President of the United States of America is vacant for a single day. Urban legend instead holds that David Rice Atchison David Rice Atchison

David Rice Atchison was a mid-19th century Democratic [i] United States Senator [i] ... 

, President pro tempore of the United States Senate was President ''de jure'' for a single day.

1911   Following the resignation and death of William P. Frye William P. Frye

William Pierce Frye was an American politician [i] from the U.S. state [i] ... 

, a compromise is reached to rotate the office of President pro tempore of the United States Senate.

1947   President Harry S. Truman Harry S. Truman

Harry S. [i] Truman was the thirty-third President of the United States [i]; as ... 

 signs the Presidential Succession Act into law which places the Speaker of the House and the Senate President Pro Tempore President pro tempore of the United States Senate

The President pro tempore of the United States Senate is the second-highest-ranking official of the ... 

 next in the line of succession after the United States Vice President.