Zollverein (Ger. Zoll Duty Customs, And Verein, Union), an association of German states for the purpose of levying uniform customs upon merchandise imported from abroad, and establishing internal free trade. It was contemplated in art. 19 of the compact of the Germanic confederation, and was actually commenced by Prussia, which in May, 1818, proposed to suppress all interior custom houses, and to protect domestic industry and assure revenue to the treasury by levying duties equivalent to 10 per cent, ad valorem on all foreign manufactures, of which nothing was to be prohibited, and on this basis to establish reciprocal free trade with other states. It was inaugurated in 1819, and was gradually joined by a majority of the states. In 1865 Austria, the two Mecklenburgs, and the Hanse towns were the only states that had not joined it. Separate treaties equalized the taxation of various members of the union. The maximum of duties on imports, according to the Prussian tariff of 1818, remained at 10 per cent, ad valorem; but the special imposts varied from time to time, and in 1851 the raw materials of manufactures were made free, or comparatively so. Each state guarded the frontiers which divided it from foreign countries, and provided for the collection of duties within its borders.

The receipts from this source were paid into a common treasury, out of which the expenses of guarding and collecting were defrayed. Export and transit duties were also levied. The net revenue was distributed in proportion to population, for which purpose a general census was taken every three years. Each state received a greater revenue from customs than it did before joining the Zollverein. The plenipotentiaries of the respective states met in June every year to settle accounts and consider proposed changes in the tariff. The immense progress of trade and industry under this union is described in the article Germany, vol. vii., p. 748. The Zollverein treaty of May 16, 1865, was intended to last from Jan. 1, 1866, till 1877, but was abrogated by the war with Austria. A new treaty with the North German confederation was concluded, July 8, 1867, by Bavaria, Würtemberg, Baden, and Hesse-Darmstadt. It went into operation on Jan. 1, 1868, and included a total population of about 39,000,000. Import duties were reduced, most articles being admitted free. Foreign trade was promoted by treaties with the principal commercial nations, and a treaty with Austria was concluded early in 1868. The union was administered by a council and a parliament.

The council consisted of delegates of its various members under the control of Prussia. In the parliament Prussia had 17 votes, Bavaria 6, Saxony 4, "Würtemberg 4, Baden 3, Hesse 3, Mecklenburg-Schwerin 2, Brunswick 2, and the other states 1 each; total, 58. The parliament was convened by Prussia at the demand of one third of the members of the council, and first met in Berlin in the spring of 1868. The Zollverein constituted a powerful bond between northern and southern Germany, paving the way for political consolidation, and was merged in the empire. The latter now forms one customs and commercial union, excepting a few peculiarly situated localities, and the free ports of Hamburg and Bremen, but including, besides the states of the empire, the grand duchy of Luxemburg and the Austrian commune of Jungholtz on the S. frontier of Bavaria. - See Der deutsche Zollverein, by W. Ditmar (2 vols., Leipsic, 1867), and L'Allemagne économique, ou Histoire du Zollverein allemand, by Emile Worms (Paris, 1874).