1. 1924: The first radio transmission of a presidential address occurred on April 23, when President Calvin Coolidge spoke to the nation from the White House.

2. 1968: On April 23, riots broke out in Washington, D.C. following the assassination of civil rights leader Martin Luther King Jr. The riots continued for several days and resulted in widespread damage and numerous deaths.

3. 1979: The Washington Post won a Pulitzer Prize for its coverage of the Watergate scandal on April 23. The award recognized the newspaper's investigative reporting that ultimately led to the resignation of President Richard Nixon.

4. 1997: On April 23, the District of Columbia changed its nickname from "the Nation's Capital" to "the American Experience." The new nickname was adopted as part of a campaign to promote tourism in the city.

5. 2010: President Barack Obama signed the Affordable Care Act, also known as Obamacare, into law on April 23, 2010. The law aimed to provide affordable health insurance for all Americans and expanded Medicaid coverage to millions of low-income individuals.