For what purpose did Columbus, landing on the coast of America, unfurl the royal flag?

This is due to the fact that during the voyage Columbus actually fulfilled the will of the Spanish monarchy, which financed the expedition. First of all, this navigator promised to find new trade routes. Forts and trading settlements were often built at remote trading points. By unfurling the royal flag, Columbus announced the appropriation of new possessions to Spain and the trade monopoly of this kingdom.