Hangul Day (한글날) is October 9, and most people know King Sejong as the man who gave Korea its alphabet. That alone would earn him a place in history. But he wasn't called "the Great" for just one thing.
Who is "Sejong the Great”?
The Joseon Dynasty had 27 kings. Only one is on the 10,000 won bill, and only one sits in gold at the heart of Seoul, in Gwanghwamun Square. Koreans call him Sejong the Great (세종대왕).
He wasn't even supposed to be king. Born in 1397, he was the third son of King Taejong, and the throne should have gone to his eldest brother. Their father chose the bookish, brilliant third son instead.
In 1418, at 21, Sejong was crowned in Geunjeongjeon (근정전), the throne hall of Gyeongbokgung Palace. He ruled until his death in 1450.
Geunjeongjeon, the throne hall of Gyeongbokgung Palace, where Sejong was crowned in 1418. The hall standing today was rebuilt in 1867. Behind the throne is the Irwolobongdo (일월오봉도), the sun, moon, and five peaks screen that stood behind every Joseon king.
So what did he do to earn the title? The short answer is Hangul. The long answer is the rest of this post.
Hangul was just the beginning
In 1443, Sejong created Hangul (한글), an alphabet simple enough to learn in days. He published it in 1446 in a book called Hunminjeongeum (훈민정음), "the proper sounds for instructing the people." We told that story in our Hangul blog.
But his list of "firsts" for ordinary people runs much longer: science, farming, welfare, even public opinion. He didn't build everything with his own hands. He found the right people, backed their work, and pushed the results out to the whole country.
Think Da Vinci's curiosity with a king's power to act on it. (Da Vinci was born in 1452, two years after Sejong died.)
Hunminjeongeum Haerye (훈민정음 해례), the 1446 book that explained the new letters. This section gives example words for each one.
Here are six things that happened on his watch.
1. The rain gauge (측우기), 1441
In a farming nation, rain meant survival. But rainfall was judged by rough estimates that changed from place to place.
In 1441, the court introduced an iron cylinder to catch and measure rain, an idea credited to Sejong's son, the crown prince. By 1442, standardized gauges were in use across the country, and every region reported its rainfall the same way.
Rain gauge stand. No rain gauge from Sejong's time survives. This stone stand, carved with 測雨臺 ("rain gauge stand"), dates to 1770, when a later king revived the system.
2. The self-striking water clock (자격루), 1434
Korea already had water clocks, but someone had to watch them all night and sound the hours by hand. Built by Jang Yeong-sil (장영실), the Jagyeongnu did it automatically with a bell, gong, and drum.
Unlike a sundial, it worked at night and on rainy days, and it kept the official time for the kingdom.
Surviving parts of a Jagyeongnu rebuilt in 1536, about a century after the original.
3. The farmer's handbook (농사직설), 1429
Earlier farming books came from China, written for Chinese soil and Chinese weather. Sejong had his provincial governors ask experienced Korean farmers what actually worked in their regions.
The result was Nongsa Jikseol (농사직설), "Straight Talk on Farming." It was published in 1429 and sent to officials across the country the following year. It is considered the first farming book written for Korean soil and seasons.
A later copy of Nongsa Jikseol. The handwritten note records it as a royal gift to a local official in 1581.
4. He asked the people first, 1430
Before changing the land tax, Sejong did something almost unheard of for a 15th-century king. He asked.
Over about five months in 1430, officials collected opinions from more than 170,000 people, from high officials to village farmers. About 98,000 were in favor and about 74,000 were against. It is often called one of the world's earliest public opinion polls.
The best part: a majority said yes, and Sejong still didn't rush. With that many people opposed, he kept testing and revising the plan. The new tax law wasn't finalized until 1444.
Rice farming in a Joseon-era painting.
5. Maternity leave, 600 years ago
In 1426, exactly 600 years ago this year, Sejong raised leave for new mothers from 7 days to 100. These weren't noblewomen. They were women enslaved to government offices (관비), at the very bottom of Joseon society.
In 1430, he added a month of rest before the birth. In 1434, he gave their husbands 30 days of leave too, so someone would be home to care for mother and baby.
A mother nursing her baby, a detail from "Lunch" (점심) by Kim Hong-do (김홍도), late 18th century.
6. Talent over birth
Remember Jang Yeong-sil, the man who built the water clock? He was born a government slave in Dongnae, in today's Busan. In Joseon, that should have decided his whole life.
Sejong saw his gift for engineering, freed him, and gave him a post at court, even though some of his ministers objected. In a society ruled by social class, that was almost unthinkable. Some of the greatest inventions of the age came from that one decision.
Jang Yeong-sil and King Sejong in the movie "Forbidden Dream" (천문), 2019.
Remembering his legacy
Koreans celebrate him twice a year. His birthday, May 15, is Teachers' Day (스승의 날), honoring his love of learning. And October 9 is Hangul Day, celebrating the alphabet he created so that ordinary people could read and write.
So the next time you spot the 10,000 won bill, or stand in front of the golden statue in Gwanghwamun Square, you'll know it isn't only about an alphabet. It's about a king who kept asking one question: what do my people need?
Happy Hangul Day.
The statue of King Sejong in Gwanghwamun Square, Seoul.