Grand-Lahou Department was created in 1988 as a first-level subdivision via a split-off from Abidjan Department.

In 1997, regions were introduced as new first-level subdivisions of Ivory Coast; as a result, all departments were converted into second-level subdivisions. Grand-Lahou Department was included in Lagunes Region.

In 2011, districts were introduced as new first-level subdivisions of Ivory Coast. At the same time, regions were reorganised and became second-level subdivisions and all departments were converted into third-level subdivisions. At this time, Grand-Lahou Department became part of Grands-Ponts Region in Lagunes District.
here is some text about Grand-Lahou Department, What year did Grand-Lahou become part of Lagunes District?
In 2011.