The town of l'Isle-sur-le-Doubs was formed from the merging of the villages of Fusnans, Carnans, and Uxelles. It belonged originally to the abbey of Les Trois Rois, and was then ceded to the Count of Neufchâtel, who built his castle there in 1230, only the foundations of which remain.
Population
The inhabitants of the commune are called l'Islois.