In an American tradition that stretches back to the '50s, the first Thursday in May marks the annual National Day of Prayer.

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The main event will be in Washington, D.C., where faith leaders will lead prayers for the country's leaders according to IBTimes.

Here are five things to know about the National Day of Prayer, according to nationaldayofprayer.org:

  1. It was started in 1952 with a bill initiated by Conrad Hilton of Hilton Hotels and Sen. Frank Carlson that required the President, which was Harry Truman at the time, to set aside a day of prayer on a day other than a Sunday.
  2. The first National Day of Prayer observance organized by the National Prayer committee occurred in 1983 at Constitution Hall, featuring then-Vice President George Bush as a speaker.
  3. In 1988, Ronald Reagan signed a law designating the first Thursday in May as the annual National Day of Prayer.
  4. President Bill Clinton signed a law in 1998 that required the president to proclaim the day every year as a day that people of the United States may turn to God in prayer and meditation at churches, in groups and as individuals.
  5. 2016 marks the 65th anniversary of the National Day of Prayer.

Click here to read more facts about religion in America from Pew Research.