Léman also included districts that were previously part of the departments of Mont-Blanc (northern Savoy) and Ain (the Pays de Gex).

The department was subdivided into the following three arrondissements and cantons:[1] After the final defeat of Napoleon in 1815, the former Republic of Geneva became a Swiss canton, and Savoy was returned to the Kingdom of Sardinia.

The Pays de Gex returned to the department of Ain except for six communes (Pregny, Collex-Bossy, Grand-Saconnex, Vernier, Meyrin and Versoix), which were ceded to the Canton of Geneva.

[3] The Prefect was the highest state representative in the department.

The office of Subprefect of Genève was held by the Prefect until 1811.