Seonunsa tradition says that the monk Geomdan founded the temple in 577, during the reign of King Wideok of Baekje. Temple and county accounts say that he taught nearby residents to make salt and that they later offered salt to the temple in gratitude.
This is a local foundation tradition rather than a fully documented historical event. It is best understood as a story long shared by Seonunsa and nearby salt-making communities.