Frankfort-on-the-Main (Ger. Frankfurt-am-Main), a wealthy commercial city in the Prussian province of Hesse-Nassau, long a free city, the place of election of the German emperors, and seat of the Diet (1816-66), is situated on the right bank of the Main, 22 miles from its confluence with the Rhine at Mainz, and 112 SE. of Cologne by rail. Pop. (1800) 40,000 ; (1875) 103,315 ; (1900) 288,989. The fortifications have given place to ornamental promenades; the river is bordered by broad quays; and the ancestral house of the Rothschilds is now the solitary relic of the famous Juden-Gasse, the ghetto of Frankfort. The Gothic Romer or town-house (1405-16) contains the Kaisersaal or imperial hall. The coronation took place in the cathedral of St Bartholomew (13th to 16th centuries). The palace of the Prince of Thurn and Taxis (1730) was the meeting-place of the North German Diet, while the Constituent Assembly of 1848-49 met in the church of St Paul. The Saalhof stands on the site of an earlier palace of the Carlovingian kings; the chapel dates from the 12th century. The new exchange was opened in 1879, the opera-house in 1880, and there are several other imposing new public buildings. One of the squares is adorned with a statue of Goethe, a native ; in another is the elaborate Gutenberg monument, commemorating the invention of printing. Frankfort is connected with the suburb of Sachsenhausen, on the left bank of the Main, by seven bridges (three railway bridges), the oldest of which was built in 1342. The city lies at the junction of seven rail-ways, which since 1888 have converged in the new Central Station, one of the largest and handsomest in Europe. Its commerce has at all times been considerable; and in the 16th century its spring and autumn fairs were among the most important in Europe. The chief articles of trade are colonial wares, iron and steel goods, leather, hides, skins, coals, wine, and beer. The manufacturing industry has largely developed since the town became Prussian. Sewing-machines and other machinery, chemicals, soap and perfumery, iron goods, straw and felt hats are among the chief manufactures. Its chief importance, however, is due to its position as one of the leading money-markets of the world.

The capital from 843 till 889 of the eastern Prankish kingdom, and the place of election of the German emperors from 1152, Frankfort in 1257 was made the first free city of the German empire, and it also became the most important. The city embraced the Reformation in 1530 ; for awhile lost its independence (1810-13); and in 1866, having espoused the Austrian cause in the seven weeks' war, was seized by the Prussians, and incorporated with Prussia. The peace of Frankfort, which ended the Franco-German war of 1870-71, was signed 10th May 1871 at the Swan Hotel by Prince Bismarck and Jules Favre. See works by Home and Grotefend (1882-84).