Prussia (Ger. Preussen), by far the most important state in the German empire, is a kingdom embracing nearly the whole of northern Germany, and owning also Hohenzollern (q.v.) and thirteen other detached territories lying within the bounds of other German states. The area is 136,000 sq. m. (one-tenth larger than the United Kingdom, or half the size of Texas), with (1900) 34,472,509 inhabitants - nearly two-thirds of the entire German empire, with three-fifths of the population. There are fourteen provinces - East and West Prussia, Berlin (city), Brandenburg, Pomerania, Posen, Silesia, Saxony, Sleswick-Holstein, Hanover, Westphalia, Hesse-Nassau, Rhenish Prussia, and Hohenzollern. About one-fifth of the present area has been acquired since 1853, the largest gains after the victorious war of 1866. The Prussia of Frederick the Great embraced only 47,800 sq. m. when he ascended the throne, and 75,000 when he died. Pop. (1819) 10,981,934; (1864)19,254,649; (1871)24,689,252.

More than two-thirds of Prussia belongs to the north European plain, already described at Germany, while less than a third, chiefly in the south-west, is hilly or mountainous. The Schnee-koppe (5250 feet) in the Reisengebirge is the loftiest summit. The western and south-western parts of the country, comprising Rhenish Prussia, Westphalia, and Hesse-Nassau, cut off by the Teutoburgerwald, the Weser Hills, the Harz, etc, from the sandy and heathy wastes of the north, are quite distinct in their physical character from the rest of Prussia. They are divided by the Rhine into two portions. The soil is generally poor in these districts also, though they possess special sources of wealth in their iron and coal mines. The level country between the Rhone and the Maas, bordering the Eifel, is extremely fertile; and Hesse-Cassel is particularly so. Nassau is specially famous for its Rhine wines. The northern plain is watered by five large rivers - the Niemen, Vistula, Oder, Elbe, and Weser - all of which rise beyond the borders of the kingdom, and the Pregel, Eider, and Ems, which are exclusively Prussian. In the west the chief river is the Rhine. About 12,000,000 persons are engaged in agriculture. Of the total area, 50 per cent. is occupied by arable land, 9 1/2 per cent. by meadows, and 11 per cent. by pasturage. The forest-lands, chiefly in East Prussia, Posen, Upper Silesia, Westphalia, Southern Hanover, and Hesse-Nassau, occupy 10,000,000 acres. The mineral products include, coal, iron, lead, zinc, copper, cobalt, antimony, manganese, arsenic, sulphur, alum, nickel, black lead, baryta, gypsum, slate, lime, freestone, salt, amber, agate, jasper, onyx, etc. Prussia yields about one-half of the annual zinc production of the world; and of the total output of coal in Germany, Prussia produces 93 per cent. The chief coalfields are in Silesia, Westphalia, and Rhenish Prussia, which are at the same time the chief industrial provinces of the kingdom. The region of the Harz in Hanover is also famous for its mining industries. All metals, salt, precious stones, and amber found along the Prussian coast from Danzig to Memel belong to the crown. Prussia has upwards of 100 mineral springs, of which the most noted are those of Aix-la-Chapelle, Ems, Schwalbach, Wiesbaden, Schlangenbad, and Selters. The principal manufactures are linens and cottons, also silk, wool, mixed cotton and linen fabrics. Other great industries are the preparation and manufacture of iron, steel (the steel and gun works of Krupp, at Essen, being world-famous), and other metallic wares, paper, leather, soap, oil, cigars, tobacco, beer, chicory, starch, beetroot, gunpowder, and glass. Berlin and Elber-feld rank as the two most important centres of manufacture on the Continent. The commerce of Prussia is materially facilitated by her central European position, and the network of river and canal navigation, which makes her territories the connecting medium between several of the great European states, and which, with 21,120 miles of railway, 50,500 miles of public roads, and a coastline of 1000 miles, gives her a free outlet to the rest of the world. About seven-eighths of the population of Prussia are Germans. Of the Slavonic tribes the most numerous are Poles, numbering 2 1/2 millions. In Brandenburg and Silesia there are about 85,000 Wends; in East Prussia upwards of 150,000 Lithuanians; the western part of the kingdom has 10,000 Walloons, using the French language; intermixed in its generally German population Silesia has 55,000 Czechs or Bohemians; Sleswick-Holstein, 140,000 Danes - making in all about 3 millions who do not use the German language, or who employ it only as secondary to their native tongues. The dominant religion is Protestantism, and since 1817 the Lutheran and Reformed Churches have been united under the head of one common Evangelical Church. The Protestants are over 64 per cent. of the population, Roman Catholics about 34, and Jews over 1. Education is widely diffused, thorough, and compulsory, between the ages of six and fourteen. Prussia has ten universities - viz. Konigsberg, Berlin, Greifswald, Breslau, Halle, Gottingen, Munster, Bonn, Kiel, and Marburg, which number above 1600 professors and teachers and 18,200 students; see Germany. In addition to the libraries of the several universities there is the Royal Library at Berlin, with 800,000 volumes and about 15,000 MSS. Since 1848 Prussia has a Herrenhaus, or House of Lords, comprising princes, the heads of the nobility, some life peers, and a few representatives of provinces, large towns, universities, etc.; and a Chamber of Deputies of 433 elected members. The monarchy is hereditary in the male line, and is now conjoined with the dignity of German emperor. The sovereign and royal family must profess the evangelical confession of faith. In the year 1905 the budget-estimate of the receipts was 2,803,805,050 marks (£140,190,252), just balanced by the expenditure. The total national debt is over £351,752,322. The Prussian contingent is the most important part of the German army, which is all under the command of the emperor-king. For the army, navy, etc, see Germany.

The Baltic lands now forming an important part of Prussia, were originally inhabited by the Slavonic Prussians, akin to the Lithuanians, who resolutely resisted all attempts of the dukes of Poland to christianise them, and were only converted by the warlike measures of the Teutonic Knights, who in 1230-83 became masters of the region, and gradually peopled it with German colonists. The knights, often at war with Poland and Lithuania, declined in power in the 14th and 15th centuries, and in 1466 had to cede West Prussia to Poland, holding the rest as fiefs of the Polish crown. In 1511 the knights elected a Hohenzollern prince as their head, who ultimately became Duke of Prussia. In 1618 the inheritance fell to another branch of the Hohenzollern house, which had since 1319 been margraves and ultimately electors of Brandenburg. Pomerania and parts of Franconia and other districts had already made the electorate a powerful state, which, however, suffered terribly in the Thirty Years' War. The 'Great Elector,' Frederick William, succeeded after 1640 in restoring prosperity, and made the electorate a European state, which in 1703 was recognised as a kingdom. Frederick the Great (1740-86) greatly aggrandised the state by his wars and administration, obtaining all West Prussia at the first partition of Poland. The second and third partitions were carried out under Frederick William II. (1786-97). Frederick William III. (1790-1840) had the difficult task of re-organising Prussia after the misery and ruin of the French occupation; after Waterloo Prussia regained almost all she had lost by the humiliating peace of Tilsit in 1807. The troubles of 1848 did not affect the area, which was added to under William I. and Bismarck by the incorporation of Hanover, Hesse-Cassel, Nassau, Frankfort, part of Hesse-Darmstadt, and Sleswick-Holstein, after the Austro-Prussian war of 1866, another result of which was that Austria ceased to be any part of Germany, and Prussia became the predominant German state. The Franco-German war of 1870-71 gave Prussia still greater predominance and the impevlal crown. See books quoted at Germany, and the history by Tuttle (Boston, 1888).