Stories by FactCheck.org

The Groundhog Day tradition was brought to the United States by German immigrants who settled in Pennsylvania, and it has its roots in the Christian Candlemas Day.
Source: Punxsutawney Groundhog Club

Oxfam International, founded in 1995 by nongovernmental groups, has 13 member organizations based in Australia, Belgium, Canada, France, Germany, Great Britain, Hong Kong, Ireland, The Netherlands, New Zealand, Quebec, Spain and the United States.

Source: Oxfam International

Chikungunya fever is caused by a virus spread by infected mosquitoes. In recent years, cases have been reported in parts of Asia and the Indian Ocean.
Source: CDC

Any donations to Haiti relief efforts made this year (by Feb. 28) can be taken as a deduction against 2009 taxes.
Source: IRS

Thomas Jefferson was the first president to deliver a "State of the Union" message in writing, instead of personally before a joint session of Congress. Subsequent presidents followed suit, until 1913, when President Woodrow Wilson made the speech in person. 
Source: Congressional Research Service

The opposition party’s response to the State of the Union address began in 1966 when Republican Sen. Everett Dirksen of Illinois and Republican Rep. Gerald R. Ford of Michigan delivered the rebuttal to President Lyndon Johnson’s speech. 
Source: Office of the Clerk of the U.S. House

The "State of the Union address" was formally known as the "Annual Message" from 1790 until 1934.
Source: Office of the Clerk of the U.S. House

Article II, Section 3, Clause 1 of the U.S. Constitution authorizes the president to deliver information on the "State of the Union" to Congress. 
Source: U.S. Constitution