After the defeat of the Prussian Army by the French at the Battle of Jena–Auerstedt, the Treaty of Tilsit in 1807 made the easternmost portion of today’s Westphalia part of the French client Kingdom of Westphalia until 1813, when the kingdom was dissolved by the Russians. While this state shared its name with the historical region, it only contained a relatively small part of Westphalia, rather consisting of mostly Hessian and Eastphalian regions.
Following to the Congress of Vienna, Prussia received a large amount of territories in the Westphalian region and created the Province of Westphalia in 1815. After in 1816, the former Duchy of Westphalia and the counties of Wittgenstein and in 1851 the condominium of Lippstadt had joined the province, Westphalia had received its modern territorial shape. In 1816, the governmental districts of Arnsberg, Minden and Münster were created.