Allier is one of the original 83 departments created during the French Revolution on 4 March 1790 with Moulins as its capital. It was formed from most of all the former province of Bourbonnais (the Duchy of Bourbonnais);
Saint-Amand-Montrond, in the Cher department, was the only part of the old province that was not made part of Allier.
It was divided in seven districts: Cérilly, Moulins, Le Donjon, Cusset, Gannat, Montmarault and Montluçon.
In 1800, with the creation of the arrondissements in France, the seven districts were changed into four arrondissements: Moulins, Gannat, Lapalisse and Montluçon.
On 10 September 1926, the arrondissement of Gannat was eliminated and in 1941 Vichy became the capital of one arrondissement of the department instead of Lapalisse.
In 1940, during World War II, the city of Vichy was the capital of Vichy France.