Founding of Baekje
Also called: Onjo legend, Biryu and Onjo
Onjo, who had come south from Goguryeo, founded Baekje with its capital at Wiryeseong on the Han River.

According to the Samguk sagi, Jumong’s son Onjo came south with his brother Biryu and founded a state at Wiryeseong in 18 BCE. When Yuri, Jumong’s son from North Buyeo, arrived and was made crown prince, the two brothers left with ten retainers and their followers. Biryu settled by the sea at Michuhol (today’s Incheon), and Onjo made his capital at Wiryeseong south of the Han, naming his state Sipje. Michuhol’s soil was damp and its water salty; after Biryu died his people moved to Wirye, and the state was renamed Baekje.
The Samguk sagi also records a variant that names Biryu as founder. The royal house’s claim to Buyeo and Goguryeo descent shows again when King Seong renamed the state Southern Buyeo. Baekje united migrants from Goguryeo with the people of the Han River basin.
The stone-mound tombs at Seokchon-dong in Seoul, built like early Goguryeo tombs, are cited as evidence of the founders’ northern origin. Fertile land and sea routes let Baekje grow early.