The current town of Allada corresponds to Great Ardra (also called Grand Ardra, or Arda), which was the capital of a Fon kingdom also called Allada (the Allada kingdom), which existed from around the 13th or 14h century (date of the initial settlements by Aja people, reorganized as a kingdom circa 1600) until 1724, when it fell to the armies of neighbour Kingdom of Dahomey.
The present-day commune of Allada covers an area of 381 square kilometres and as of 2002 had a population of 91,778 people.
In the mid-sixteenth century, Allada (then called Grand Ardra, or Arda) had a population of about 30,000 people.
The original inhabitants of Ardra were ethnic Aja.
According to oral tradition, the Aja migrated to southern Benin around the 12th or 13th centuries, coming from Tado, on the Mono River. They established themselves in the area that currently corresponds to southern Benin, until circa 1600, when three brothers – Kokpon, Do-Aklin, and Te-Agdanlin – split the rule of the region amongst themselves: Kokpon took the capital city of Great Ardra, reigning over the Allada kingdom, while his brother Do-Aklin founded Abomey (which would become capital of the Kingdom of Dahomey) and their brother Te-Agdanlin founded Little Ardra, also known as Ajatche, later called Porto Novo (literally, "New Port") by Portuguese traders (which is the current capital city of Benin).
^Asiwaju, A. I. (1979). "The Aja-Speaking Peoples of Nigeria: A Note on Their Origins, Settlement and Cultural Adaptation up to 1945". Africa: Journal of the International African Institute49 (1): 15. doi:10.2307/1159502. ISSN0001-9720.