The present-day commune of Allada covers an area of 381 square kilometres and as of 2013 had a population of 127,512 people.

[1] In the mid-sixteenth century, Allada (then called Grand Ardra, or Arda) had a population of about 30,000 people.

[3] According to oral tradition, the Aja migrated to southern Benin around the 12th or 13th century, coming from Tado, on the Mono River in modern Togo.

They established themselves in the area that currently corresponds to southern Benin, until c. 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(Little Adja), later called Porto Novo (literally, "New Port") by Portuguese traders (which is the current capital city of Benin).

The Haitian revolutionary Toussaint L'Ouverture, who was the grandson of the Allada prince Gaou Guinou, was the founding father of the Republic of Haiti.