Mainz (Ger. pron. Mintz; Fr. form Mayence; old-fashioned English form Mentz), an imperial fortress of the first rank, in the grand-duchy of Hesse, on the left bank of the Rhine, opposite the junction of the Main, 22 miles WSW. of Frankfort. The Rhine is here crossed by a stone bridge (superseding in 1885 the former pontoon bridge) to the village of Kastel, included in the fortifications, and by an iron railway bridge, 140 yards long, to the port of Gustavsberg, at the mouth of the Main. op. (1875) 56,421; (1900) 84,251, of whom two-thirds are Roman Catholics ; in the 14th century it is said to have reached 90,000. Mainz is one of the most ancient cities in Germany ; but its oldest part, Kastrich, has been rebuilt in a modern style since its almost total destruction in 1857 by the explosion of a powder-magazine; while a handsome new quarter has sprung up on the north, in the space afforded by the advancing of the fortifications in 1874. The cathedral, originally built in 978-1009, was thrice destroyed by fire, and dates in its present form from the 13-14th century. In 1870-78 it was thoroughly restored, and the present central Romanesque tower, 270 feet high, built. There are also the 18th-century palace of the grand-duke, an arsenal of 1736, and the large red-sandstone electoral palace, with a library of 150,000 vols., and the Romano-German Museum, a matchless antiquarian and historical collection. Mainz is an important centre of the Rhine trade with Holland and Belgium, and also carries on a very large transit trade by railway. Great harbour-works, docks, and storehouses, were opened in 1887 at a cost of 250,000; while the Rhine is skirted by a broad quay, four miles long. Furniture, leather goods, machinery, musical instruments, chemicals, gold and silver ware, hats, soap, etc, are among the manufactures; and brewing, printing, and market-gardening in the environs are also important industries. In 13 B.c. Drusus built here the fort of Mogunt-iacum or Maguntiacum. The real importance of the town dates, however, from the Frank-ish emperors. In the 13th century Mainz was the head of the confederacy of the Rhenish cities, but in 1462 it was added to the domains of the archbishops of Mainz, the premier spiritual electors of the empire. The city was several times in the possession of France, notably in 1801-14. In 1816 it was assigned to Hesse-Darmstadt, but to remain a federal stronghold, garrisoned by Prussian and Austrian troops. After 1866 it was held by Prussian troops, until in 1870 it was declared an imperial German fortress. Mainz was the birthplace of Gutenberg.