How did Spain received all French land west of the Mississippi?

Spain received all French land west of the Mississippi through the Treaty of Fontainebleau in 1762, during the French and Indian War. As France faced defeat, it ceded its territories in North America to Spain in a secret agreement to prevent them from falling into British hands. This transfer was later formalized in the Treaty of Paris in 1763, which ended the war and recognized Spain's claim to the Louisiana territory.