evolving names

[letterman]

When did Koryo become Chosun and what was before Koryo???

[FrederickII]

General Yi Song Gye (a descendant of Yi Ui Bang's younger brother), a general of Koryo, overthrew the Koryo dynasty and formed Choson.

Before Koryo there was Shilla, Wang Gun a Silla general forced Shilla to surrender (imagine surrendering a 1000 year old dynasty)

Before Shilla Korea was divided into many warring states. Baekjae, Koguryo (not to be confused with Koryo) Shilla were the most powerful though there were other Korean kingdoms in Manchuria and on the pennensula. With Chinese help Shilla managed to conquor the other kingdoms.

The survivors of Koguryo formed a state in Manchuria which was destroyed by Khitan after a couple hundred years.

Finally Choson was destroyed by South Korea's president Rhee.

[donilpark]

Hwanguk (mythical)

Baedal (mythical)

Gochosun (Actually, it's just Chosun, but we refer to this Chosun as ancient (Go) Chosun to distinguish it from the Chosun that comes later)

Bukbuyo (Norther Buyo), Choissinakrangguk, Namsamhan (Three Southern Hans), Dongokjeo

Koguryo (A.K.A Koryo), Baekje (A.K.A Nambuyo, Southern Buyo), Shilla, Gaya

Balhae (A.K.A. Koryo or Daejin), Unified Shilla

Later Baekje, Shilla, Koryo

Koryo

Chosun

Daehanjeguk (Korean empire)

Chosun (reverted back to Chosun from Daehanjeguk during the Japanese occupation)

Temporary Government in Shanghai

Daehanminguk/Hanguk (Republic of Korea), Chosun Minjujuui Inmin Gonghwaguk/Bukchosun (People's Republic of Korea)


I left many out as well, such as Tamra, that was in present day Jeju island.
Ones that are on the same line were in existence for pretty much the same period with each other.
Koguyo and Koryo are some of the variants of one same name.
So you can see dynasties like Koryo, Choson, later Baekje, Balhae all tried to show their orthodoxy by using the same name as one of the ancestral states.
The Western name of Korea, 'Korea' comes from Koryo/Koguryo as well. Today, this name is used in part becuase of its political neutrality.
To answer the question, by the way, Koryo was overthrown by Chosun in 1392.