If you haven't spent your entire school career watching baby goat videos on your phone, you've heard the name Dr. Martin Luther King, Jr. by now. You're probably grateful that you get a day off from school in his honor. But though it might be hard to believe, that isn't his greatest legacy. What could be greater than a weekday off, you ask? Oh, you know, furthering the causes of equality, brother/sisterhood, universal love and compassion, social justice, and true democracy.

Okay, at least it's on par with the day off.

Even though segregation was found to be unconstitutional in the Supreme Court case of Brown v. Board of Education in 1954, it was a way of life in the South well through the early 1960s. White and Black Americans were separated as much as the racists in charge could manage, and there were whites-only hotels, restaurants, and bathrooms that were off-limits for African Americans. In thousands of communities, Blacks were denied the right to vote, the right to an adequate education, and basic economic opportunity by local governments, corporate institutions, and a general culture of hate.

And segregation wasn't just the local law. It was enforced through violence and intimidation. Black homes and churches were bombed by white supremacists, the KKK and White Citizens' Councils had a strong public presence, and racial slurs and vigilante murders were commonplace in public life.

Overall verdict: just plain bad.

Birmingham, Alabama was one of the worst places in America to be a Black American, so the Southern Christian Leadership Conference (Dr. King's crew, the SCLC) decided to go there to demonstrate against the segregation laws. They did, and according to plan, many people were arrested.

Dr. King, one of the heroes of this story, was among them.

While he was resting in the cozy confines of the Birmingham City Jail on the charge of "parading without a permit," he had the pleasure of reading a statement in the local paper written by some white clergymen. It said Blacks should just put up with their miserable situation until everything was "resolved" in the racist local courts. After all, isn't that what Jesus would do?

Here's a hint: no.

The clergymen called MLK an "outsider" (from the distant land of Atlanta) and portrayed him and the rest of the activists as a bunch of rabble-rousers. As if that wasn't enough, they commended the police for being so reasonable and gentle with the protestors (they might have had a point if the Birmingham police used Corgis instead of German shepherds). Stay out of the streets, Black people, they said. Be patient.

Some of this might sound familiar…

Well, there was a lot of this kind of talk going around back then. Dr. King and his colleagues didn't usually pay much attention to it, but as you can imagine, MLK suddenly found himself with a lot of free time because jail. And that's how "Letter from Birmingham Jail" was born. It arguably marks the turning point of both his career and the Civil Rights Movement as a whole.

It's clear, direct, and full of profound, inspirational wisdom that you could easily quote if you wanted to look smart.

• "Injustice anywhere is a threat to justice everywhere. We are caught in an inescapable network of mutuality, tied in a single garment of destiny."
• "…it is wrong to use immoral means to attain moral ends."
• "…it is just as wrong, or even more, to use moral means to preserve immoral ends"
• "Stop being racist, people."

Actually, he might not have said that last one.

P.S. Heard this letter called something other than "Letter from Birmingham Jail?" Scoot on down to "What's Up with the Title?" to learn more. Meanwhile, put down those baby goat videos for a few minutes—Dr. King has something he wants to tell you.

Waaaay back in ancient America (1963), before we lived in today's utopia of perfect racial harmony, there used to be a thing called racism. In 1964, the Civil Rights Act took care of all that.

Yeah…no. It didn't.

It's not often that a text is almost word-for-word completely relevant fifty years later. It's tough to write something like that. You never know when the next iPhone or Snapchat or ectoplasmic fusion-powered retrocannon is gonna come around and revolutionize everything. MLK probably hoped that his strategy of non-violent civil disobedience wouldn't be needed anymore by now because his dream that everyone would just love each other already would be a reality.

Unfortunately, everyone doesn't love each other, so we still need his letter. Hate groups still flourish, employment discrimination is still alive and well, and it took until 2014 for Wilcox County High School in Georgia to hold a racially integrated prom.

And that's just for starters.

One reason we study history is to benefit from the world's greatest minds. Well, Dr. King was an intellectual powerhouse. In the philosopher's boxing ring he was heavyweight champion of world. He was as electrifying a 20th-century leader as his old namesake Martin Luther was in the 16th. His genius wasn't universally appreciated while he was alive, but nowadays most everybody tears up a little when they hear his "Mountaintop" speech or his "I Have a Dream" speech (anyone who doesn't is probably a top-secret android prototype).

Even white supremacists cry when they hear him speak…although for different reasons.

Dr. King got arrested for protesting segregation and white supremacy many times all over the South. And he wasn't doing it to Yelp different police department holding cells. He was purposely breaking the law to change the law. He was working to overturn racist laws that dictated where Black Americans could and could not sit down, or drink water, or use the bathroom—laws that enabled racists to run the South as if only white people were real legitimate human beings with feelings and hopes and dreams.

He felt the best way to confront the ignorance of racism was to disobey its silliest laws and ordinances, get a bunch of people arrested, make national headlines, get TV cameras to take a good long look at the protests, and to win a long-term public relations campaign against the local government officials and community leaders. It was a strategy that could only work if he had the truth on his side.

And he did, which was convenient.

Dr. King was one of many courageous Americans who led the movement against the soul-crushing reality of legalized racism. He was a preacher, not a politician, and that's where his power came from. He was a devout Christian who tried to live up to his understanding of teachings of Jesus. Religious or not, you've probably heard the spiel by now: love your neighbor, turn the other cheek, don't double-dip.

Today, you'd be shocked to see a "Whites Only" water fountain, or a movie theater or hotel where African Americans weren't allowed in. That's in part because of the man writing that letter in Birmingham Jail, who pleaded his case before millions of Americans and wasn't afraid to get arrested for a cause he knew was just.

Sadly, we don't get to behold the glory that would have been MLK's Twitter feed, so we'll just have to settle for the next best thing, which is everything he ever wrote.