We all know that Martin Luther King Jr. was a pivotal figure in the civil rights movement. Most of us know about his work as a pastor and his roles with the National Association for the Advancement of Colored People (NAACP) and the Southern Christian Leadership Conference (SCLC). We know he had a dream, and worked tirelessly to make that dream a reality before being assassinated in 1968. But along with the wealth of details that we do know, there are just as many intriguing details that may have sneaked by. So in honor of what would have been King's 80th birthday, let's celebrate with some lesser-known fascinating facts.

1. He was born Michael King Jr. after his father, Michael King Sr., but the senior King changed their names to Martin Luther King Sr. and Jr. when Martin Jr. was about 5 years old. By some accounts, King Sr. said that his real name was Martin Luther, but that his mother called him Michael and he didn't know; when he found out, he changed both the names.

2. The younger King was one out of only 11 African-American students in 1948 at Crozer Theological Seminary in Pennsylvania; in his third year there, he was elected class president. He graduated with honors as class valedictorian.

3. In 1963, he became was the first African-American to be named Time magazine's Man of the Year.

4. At the age of 35, he became the youngest man to have been honored with the Nobel Peace Prize. He donated the prize money of $54,123 to benefit the civil rights movement.

5. Between 1957 and 1968, he traveled more than 6 million miles and spoke at more than 2,500 events.

6. He was arrested 30 times and was awarded at least 50 honorary degrees from colleges and universities.

7. There are more than 900 streets named after him in the United States — and the number continues to grow.

8. In 1968, the first legislation was introduced by U.S. Rep. John Conyers Jr. of Michigan to make King's birthday a federal holiday. The bill was finally turned into law in November 1983 and the first official holiday was observed on the third Monday of January in 1986.

9. King is the only non-president to have a national holiday in his name, and is the only non-president with a memorial on the National Mall in Washington, D.C.

10. In 1994, Congress designated Martin Luther King Jr. Federal Holiday as a national day of service, which is led by Corporation for National and Community Service. It is the only federal holiday observed as a national day of service – a "day on, not a day off." (To find a local project for which to volunteer, visit the MLKday.gov website or try one of these ideas.)

Bonus: The famous "I have a dream" section of the monumental "I Have a Dream" speech was unscripted; although he had used the phrase before and wanted to include it, his advisor suggested that he leave it out of the speech for this occasion. Fortunately, he went with it. Watch him deliver the historic speech in the video below:

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