Goguryeo

State · 36 BCE – 681 CE · at its largest around 480 CE

Kingdom of northern Korea and Manchuria, one of the Three Kingdoms of Korea, which resisted Sui and Tang invasions before falling to a Silla–Tang alliance in 668.

On its lands while it lasted

Goguryeo (c. 37 BCE – c. 668 CE): Kingdom traditionally founded by Jumong in 37 BCE that grew to rule northern Korea and Manchuria.
Jolbon (c. 36 BCE): Capital of Goguryeo (36 BCE–3).
Baekje (c. 18 BCE – c. 660 CE): Kingdom in southwestern Korea, traditionally founded in 18 BCE, a conduit of culture and Buddhism to Japan.
Gungnae (c. 3–427 CE): Capital of Goguryeo (3–427).
Wiryeseong (c. 347 CE): Capital of Baekje (347–660).
Gwanggaeto the Great (374 CE – 413 CE): King of Goguryeo whose conquests greatly expanded the kingdom in Manchuria and Korea.
Goguryeo–Tang War (645–668 CE): Series of wars ending in the fall of Goguryeo to Tang and Silla forces in 668.