During the time between classes I decided to drop by the U of U library to see how their Korean collection was. I found three books which discussed the history of Hangeul so I decided to sit down and skim through them. I learned some pretty interesting things.
There have been multiple systems used by the Koreans have used to make sense of documents written in Chinese characters before Hangeul became prevalent. From what I saw, there were three systems that were used at one time or another. Idu used special characters to represent Korean endings and grammatical markers which were tagged onto Chinese characters. Hyangchal took Korean phrases and wrote them using Chinese to represent the Korean sounds. Gugyeol took the opposite approach from Hyangchal by going from Chinese into Korean. Chinese characters kept their original order with special subsets of Chinese characters added on them to denote grammatical terms. Finally, Hangeul was created to finally give Korean it’s own writing system rather than using a subset of Chinese.
When what we call 한글 was first invented, there were two very important documents that explained it called 훈민정음 and 훈민정음 해례. The second has a famous quote about how easy it is to learn: “A wise man can acquaint himself with them before the morning is over; a stupid man can learn them in the space of ten days.” I would definitely agree with this, Hangeul itself is so easy that there’s no excuse for ANYONE to use romanization. You can’t even image how much I HATE romanized Korean. Many of the books on that shelf used romanized Korean exclusively, and I can tell you it was ugly and confusing as heck. Whoever thought it would be good to learn Korean through English needs to rethink their strategy. If I could gather all those books together and burn them I would. I’ve said it before and I’ll say it again to those learning Hangeul. DON’T. USE. ROMANIZATION.
Anyways, getting back on track. There have been a lot of changes over the centuries. Here are some of the more interesting characters that have been dropped (Don’t even ask me how to pronounce them.):
ᄙ, ㅹ, ᄽ, ᄿ, ᇮ, ᅏ, ᅑ, ㆅ, ᄛ, ㅱ, ㅸ, ᄼ, ᄾ, ㅿ, ㆁ, ᅎ, ᅐ, ᅔ, ᅕ, ㆄ, ㆆ, ᇄ, ㅩ, ᇏ, ᇑ, ᇒ, ㅫ, ᇔ, ᇕ, ᇖ, ᇞ, ㅴ, ㅵ, ᄤ, ᄥ, ᄦ, ᄳ, ᄴ, ᅷ, ᅸ, ᅹ, ᅼ, ᅽ, ᅾ, ᅿ, ᆀ, ᆁ, ᆂ, ᆃ, ㆇ, ㆈ, ᆆ, ᆇ, ㆉ, ᆉ, ᆊ, ᆋ, ᆌ, ᆍ, ᆎ, ᆏ, ᆐ, ㆊ, ㆋ, ᆓ, ㆌ, ᆕ, ᆖ, ᆗ, ᆘ, ᆙ, ㆎ (originally vowels only had one line with one or more dots to denote which vowel it was)
Hangeul wasn’t even called ‘한글’ (meaning great script) until around 1910. Up until that time, it was called 언문 (vulgar script). The man attributed to naming it 한글, 주시경, apparently hated it being called the vulgar script. As you can imagine, the newer name really caught on with the people. Around the same time, the term 한 was becoming popular to denote Korean things.
The books go much more deeper than just these points, but you can get the gist of it in this post (hopefully). Anyways, if you’re interesting in learning more about how the Korean language developed from a spoken language to finally having it’s own written script, check out Wikipedia’s vast knowledge base or see if your l0ocal library has books on Korean.
Source: 
