OLDENBURG, a grand-duchy of Germany, with an area feld. It ranks tenth among the states of the German empire and has one vote in the federal council and three members in the reichstag.

I. The duchy of Oldenburg, comprising fully four-fifths of the entire area and population, lies between 52° 29' and 53° 44' N. lat. and 7° 37' and 8° 40' E. long., and is bounded on the N. by the German Ocean and on the other three sides by Hanover, with the exception of a small strip on the east, where it is conterminous with the territory of the free city of Bremen. It forms part of the north-western German plain defined by the Weser and the Ems, and, except on the south, where the Dammergebirge attain a height of 300 feet, it is almost entirely flat, with a slight inclination towards the sea. In respect of its soil it is divided broadly into two parts, - the higher and inland-lying " Geest," consisting of sandy plains intermixed with extensive heaths and moors, and the "marsh lands" along the coast, consisting of rich but somewhat swampy alluvial soil. The latter, which compose about one-fifth of the duchy, are protected against the inroads of the sea by dykes as in Holland ; and beyond these are the so-called " watten," generally covered at high tide, but at many points being gradually reclaimed. The climate is temperate and humid ; the mean temperature of the coldest month at the town of Oldenburg is 26° Fahr., of the warmest 66°. Storms are numerous and somewhat violent, owing to the almost entire absence of trees ; and fogs and ague are prevalent in the marsh lands. The chief rivers are the Hunte, flowing into the Weser, and the Hase and Leda draining into the Ems. The Weser itself forms the eastern boundary for 42 miles, and internal navigation is greatly facilitated by a new canal, passing through the heart of the duchy and connecting the Hunte and the Ems. On the north there are several small coast streams conducted through the dykes by sluices, the only one of importance being the Jade, which empties itself into the Jadebusen, a deep gulf affording admirable accommodation for shipping. The duchy also contains numerous small lakes, the chief of which is the DUI-lamer See in the south-east corner, measuring 4 miles in length by 2 in width. About 30 per cent. of the area of the duchy is under cultivation and 17 per cent. under pasture and meadows, while the rest consists mainly of moor and heath. The forests occupy a very small proportion of the whole, but there are some very fine old oaks. In the Geest the principal crops are rye, oats, potatoes, and buckwheat, for which the heath is sometimes prepared by burning. Large tracts of moorland are, however, useful only as producing an abundant;supply of turf and peat for fuel, or as affording a scanty subsistence to the flocks of small coarse-woolled Oldenburg sheep. The rich soil of the marsh lands produces good crops of wheat, oats, rye, hemp, and rape, but is especially adapted for grazing. The fat cattle and horses raised on it are highly esteemed throughout Germany, and the former are exported in large numbers to England. Bee-keeping is also much in vogue on the moors. The live stock of Oldenburg forms a great part of its wealth, and the ratio of cattle, sheep, and horses to the population is one of the highest among the German states. There are few large estates, and the ground is mostly in the hands of small farmers, who enjoy the right of fishing and shooting on their holdings. Game, however, is scarce; but the fishing is fairly productive. The mineral wealth of Oldenburg is very small, and there are no mineral springs.

The industries are comparatively insignificant, though recently somewhat stimulated by the extension of the railway system and other causes. Woollen and cotton fabrics, stockings, jute, and cigars are made at Yard', Delmenhorst, and Lohne ; cork-cutting is extensively practised in some districts, and there are a few iron-foundries. Trade is relatively of more importance, chiefly owing to the proximity of Bremen. The agricultural produce of the duchy is exported to Scandinavia, Russia, England, and the United States, in return for colonial goods and manufactures. Varel, Brake, and Elsfleth are the chief commercial harbours. In 1881 the ports of the The principality of Lilbeck, formed of the old bishopric Trave. The chief rivers are the Schwartau, a tributary esque, especially in the vicinity of the PlOner See and the more extensively than in the duchy of Oldenburg, about 75 per cent. of the area being cultivated. The population in 1880 was 34,973.

The principality of Birkenfeld, 194 square miles in extent, lies in the midst of the Prussian province of the Rhine, about 30 miles to the west of the Rhine at Worms covered with forests. Iron-founding, cotton-spinning, and agates, of which great numbers are found within the prin cipality (compare ONYx). Birkenfeld is traversed from in 1880 was 38,685.

The total population of the grand-duchy of Oldenburg in 1830 was 337,478, showing an increase of 1'10 per cent. per annum since the census of 1875, and an average of 136 persons to the square mile. The bulk of the inhabitants are of the Saxon stock, but to the north and west there are numerous descendants of the ancient Frisians. The differences between the two races are still to some extent perceptible, but Low German (" Platt-deutsch ") is universally spoken, except in one limited district, where a Frisian dialect has maintained itself. In general characteristics the Oldenburg peasants resemble the Dutch, and the absence of large landowners has contributed to make them sturdy and independent. Oldenburg has the credit of showing almost the lowest average of illegitimate births among the German states, amounting in 1631 to only 5 per cent. This is in significant contrast to the high rate (15 per cent.) among the semi-feudatory peasants of MECKLENBURG (q.v.). The population of Oldenburg is somewhat unequally distributed, some parts of the marsh lands eontainin ; over 300 persons to the square mile, while in the Geest the number occasionally sinks as low as 40. Nearly 80 per cent. of the inhabitants are returned as belonging to the " rural " population. The only town with more than 10,000 inhabitants is Oldenburg, the capital of the grand-duchy. The war-harbour of Wilhelmshaven, with 12,000 inhabitants, on the shore of the Jadebusen, was built by Prussia on a piece of land bought from Oldenburg. The chief towns of Birkenfeld and Liibeck are Birkenfeld and Eutin, with 2539 and 4574 inhabitants respectively. Oberstein in Birkenfeld has 4803 ; in the 12th century it was a lordship holding directly of the empire.

Oldenburg is a Protestant country, and the grand-duke is required to be a member of the Lutheran Church. Roman Catholicism, however, preponderates in the south-western provinces, which formerly belonged to the bishopric of Minster. Oldenburg Roman Catholics are under the sway of the bishop of Munster, who is represented by an official at Vechta ; and the Catholics of Birkenfeld belong to the diocese of Treves. At the census of 18S0 there were in the grand-duchy 260,416 Protestants, 74,254 Roman Catholics, and 1654 Jews. The educational system of Oldenburg is on a similar footing to that of north Germany in general, though the scattered position of the farmhouses interferes to some extent with school attendance. The proportion of Oldenburg recruits in 1382 unable to read or write was only 0'27 per cent., which compares favourably with „the average of 1'54 for the whole empire. There is no university in Oldenburg territory, but an ample supply of primary, secondary, and special schools.

The constitution of Oldenburg, based upon a decree of 1849, revised in 1852, is one of the most liberal in Germany. It provides for a single representative chamber, elected indirectly by universal suffrage and exercising concurrent rights of legislation and taxation with the grand-duke. The chamber, which consists of thirty-four members (twenty-six for Oldenburg and four for each of the principalities), meets at regular intervals of three years. The executive consists of three ministers, who are aided by a committee of the landtag, when that body is not in session. The local affairs of Birkenfeld and Lubeck are entrusted to provincial councils. All citizens are alike in the eye of the law. and all exemptions and privileges have been abolished. The municipal communities enjoy an unusual amount of independence.

The finances of each constituent state of the grand-duchy are managed separately, and there is also a fourth budget concerned with the joint administration. The last generally shows a sum of about £50,000 on each side, the expenditure including a matricular contribution of £33,500 to the imperial treasury. In the budget of 1882 the revenues of the duchy of Oldenburg, the principality of Ltibeck, and the principality of Birkenfeld were estimated at £2S9,965, £40,419, and £43 864, while the estimated expenditure was in each case somewhat less. The duchy of Oldenburg has a debt of nearly £2,000,000 and Liibeek one of £2000, while Birken- feld and the grand-duchy as a whole are free of debt. An annual allowance of about £13,000 is made to the grand-duke, and he is believed to derive as much more from his private estates. The troops of Oldenburg furnish the German army with a regiment of infantry, a regiment of cavalry, and two batteries of artillery.

Ilistory. - The earliest recorded inhabitants of this district were the Germanic Chauci, who were afterwards merged in the Frisians. Old chroniclers delight in tracing the genealogy of the counts of Oldenburg up to Wittekind, the stubborn opponent of Charlemagne ; but their first historical representative is Elimar I., who flourished at the close of the 11th century. His descendants appear as vassals of the powerful Saxon dukes, but attained the rank of independent princes of the empire on the dissolution of the Saxon power by Frederick Barbarossa (c. 1180). The courtship of Delmenhorst at this time formed part of the Oldenburg dominions, but was afterwards frequently separated front them, and was not lastingly united under the same ruler till the beginning of the 17th century. The northern and western parts of the present duchy of Oldenburg were in the hands of more or less independent Frisian princes, who had generally remained pagans ; and Oldenburg history for the next two centuries is largely concerned with feuds with these small potentates, and gradual extension of territory at their expense. Bremen and Munster were also frequently at war with the counts of Oldenburg. In 1448 Count Christian VIII. was elected king of Denmark, and, a little later, duke of Holstein and Schleswig, the latter event pregnant with important consequences for future history. Oldenburg was made over to his brother Gerhard, an ambitious prince, whose turbulent disposition resulted in an abdication in favour of his sons, forced on him by a league of Hamburg, Liibeck, and Bremen. Protestantism was introduced by Anton I. (1531-1573), who, however, remained loyal to Charles V. in the Schmalkald war, and was thus enabled to increase his territories. On the accession of Anton Gunther in the beginning of the 17th century Oldenburg and Delmenhorst were finally welded into one, and about the same period the last free Frisian states, Jever and Kniphausen, were also absorbed by Oldenburg. Anton Gunther proved himself the wisest prince who had ruled in Oldenburg, and by his prudent neutrality in the Thirty Years' War secured for his domains immunity from the devastations to which most other German states were exposed. He also obtained from the emperor the right to levy tolls on vessels passing up the Weser, a lucrative grant, which soon formed one-fifth of his revenues. On his death without issue in 1667 the succession passed to the Danish reigning house, after the claims of the Holstein-Gottorp and Holstein-Sonderburg branches of the family had been compromised. Oldenburg remained under the sway of the Danish monarchs for about a century, - a period, on the whole, of peaceful development. At length, in 1773, the Danish monarch agreed to a family compact, in accordance with which he resigned Oldenburg to the Holstein-Gottorp line in return for a renunciation on their part of all claim to Schleswig and Holstein. The head of the Holstein-Gottorp family at this time was the grand-duke Paul of Russia (afterwards the emperor Paul I.); but he handed over Oldenburg, which was now created a duchy, to his cousin Frederick Augustus, bishop of Liibeck, representative of a younger line. The bishop's son, who followed his father in 1785, was a man of weak intellect ; and his cousin, Peter Frederick Louis, who acted as administrator and eventually succeeded to the throne, is the direct progenitor of the present grand-duke. Peter had the task of managing the duchy in the troublous times of the Napoleonic wars, and, though he joined the Confederation of the Rhine, had afterwards to see his domains forcibly annexed to France on his refusal to exchange them for Erfurt. This led him to join the allies, and his services were rewarded at the congress of Vienna by the addition of Birkenfeld to his dominions, which were also raised to the rank of a grand-duchy. The secularized bishopric of Lubeck had been already added to Oldenburg in 1803. Oldenburg did not escape the revolutionary wave that swept over Europe in 1843, but no very serious disturbances took place, and the grand-duke granted a constitution in 1849. This constitution was of an ultra-liberal character, and, as the country had hitherto been ruled in the spirit of an enlightened but absolute despotism, strengthened by the absence of a privileged class of nobles, the unimportance of the towns, and the comparative independence of the peasantry, it was inevitable that it should not work at once without friction. In 1852 it had to submit to some modification, which, however, still left it one of the most liberal constitutions in Germany. In 1864 the grand-duke seemed at first inclined to insist upon his claims to the Schleswig-Holstein succession, but he ultimately resigned them in favour of Prussia. In 1866 he sided with that power against Austria, and in 1871 the grand-duchy became a member of the German empire.

See Halcm, Gesch. d. Herzogth. Oldenburg (1794-96); Runde, Oldenburgische Chronik (3d ed., 1863); Bose, Das Grossherzogthum Oldenburg (1863); Kollinann, Des Herzogthum Oldenburg in seiner wirthschaftlichen Entwickelung wahrend der letzten 25 Jahre (1879); the publications of the Statistical Bureau of Oldenburg; the annual Hof- and Staatshavibuch des Grossherzogthums Oldenburg.