Today is the National Day of Prayer, an annual day of observance celebrated by Americans of various faiths. Here are nine things you should know about the day when people are asked “to turn to God in prayer and meditation.”

1. The National Day of Prayer is an annual observance held on the first Thursday of May, inviting people of all faiths to pray for the nation. It was created in 1952 by a joint resolution of the United States Congress, and signed into law by President Harry S. Truman.

2. Prior to the nation's founding, the Second Continental Congress issued a proclamation recommending “a day of publick [sic] humiliation, fasting, and prayer” be observed by the “English Colonies” on Thursday, July 20, 1775, “and to bless our rightful sovereign, King George the Third…”

3. In his role as Commander-in-Chief of the Continental Army, George Washington acknowledged a second day of “fasting, humiliation and prayer” proclaimed by the Continental Congress to be held on Thursday, May 6, 1779. To enable his soldiers to observe the day, Washington ordered a one-day cessation of recreation and “unnecessary labor”.[12] In March 1780, Congress announced a day of “fasting, humiliation and prayer” to be held on Wednesday, April 26, 1780.

4. There have been 142 national calls to prayer, humiliation, fasting and thanksgiving by the President of the United States (1789-2013).

5. The National Observance in Washington, DC is coordinated by the National Day of Prayer Task Force, an evangelical nonprofit group. The NDP Task Force was founded in 1979 by Mrs. Vonette Bright, co-founder of the evangelical Christian organization Campus Crusade for Christ International. Since 1991, Shirley Dobson, whose husband is James Dobson, has been the chairwoman.

6. During each year of the George W. Bush Administration, events coordinated with the NDP Task Force were held in the White House. Presidents Reagan and George H. W. Bush each held only one NDP Task Force-coordinated religious ceremony on a National Day of Prayer during their tenures. During his tenure, President Clinton held informal prayer meetings but did not participate in NDP Task Force events, nor has President Obama.

7. In 2008, the Freedom From Religion Foundation sued to challenge the designation of a National Day of Prayer. In 2010, a federal judge ruled that the statute establishing the National Day of Prayer was unconstitutional as it is “an inherently religious exercise that serves no secular function.” A three judge panel of the Seventh Circuit Court of Appeals unanimously overturned that decision.

8. There have been 65 Presidential Proclamations for a National Day of Prayer (1952-2013). Gerald R. Ford (1976), George H. Bush (1989-91) and Barack H. Obama (2012) are the only U.S. Presidents to sign multiple National Day of Prayer Proclamations in the same year.

9. 34 of the 44 U.S. Presidents have signed proclamations for National Prayer. Three of the Presidents who did not sign a proclamation died while serving in office. Two Presidents, not included in the count - William Howard Taft and Warren Gamaliel Harding, signed proclamations for Thanksgiving and Prayer. Every President since 1952 has signed a National Day of Prayer proclamation.