1. In 1795, the cornerstone of the United States Capitol building was laid on April 8th. The building, which took over 30 years to complete, is a symbol of American democracy and the seat of the United States Congress.

2. On April 8th, 1864, President Abraham Lincoln signed the District of Columbia Emancipation Act, which freed over 3,000 enslaved individuals in the District of Columbia. This was an important step toward the eventual abolition of slavery in the United States.

3. In 1909, the United States Naval Observatory opened its doors in Washington, D.C. The observatory is responsible for maintaining the Master Clock, which provides precise time for the U.S. military and other government agencies.

4. On April 8th, 1948, the World Health Organization was founded in Geneva, Switzerland. The organization has played a critical role in promoting global health initiatives and combating diseases like smallpox and polio.

5. In 1968, civil rights leader Dr. Martin Luther King Jr. delivered his famous speech "I've Been to the Mountaintop" at the Mason Temple in Memphis, Tennessee. In his speech, Dr. King spoke about his vision for a more just and equal society, and encouraged his audience to continue the struggle for civil rights. Just four days later, he was assassinated in Memphis.