Hesse-Cassel , (Ger. Kurhessen, Electoral Hesse), a former German electorate, incorporated with Prussia in 1866. At the time when it ceased to be an independent state it had an area of 3,701 sq. m., and a population, according to the census of 1864, of 745,063. The principal towns were Cassel, Marburg, Fulda, Hanau, Hersfeld, Schmalkalden, and Rinteln. Hesse-Cassel was the elder branch of the Hesse dynasty, and was founded by the eldest son of Philip the Magnanimous, the landgrave William IV., surnamed the Wise (1567 to 1502). His grandson, William V., took part on the Protestant side in the thirty years' war, and his widow after the restoration of peace obtained the greater part of Schaum-burg and other territory. William VII. was succeeded in 1670 by his brother Charles, while another brother, Philip, founded the branch of Hesse-Philippsthal. Charles's eldest son became, by his marriage with Ulrike Eleo-nore, king of Sweden in 1720. In 1730 he assumed the government of his native country as Frederick I., and was succeeded in 1751 by his brother William VIII., who fought in the seven years' war on the side of Prussia. His son, the notorious Frederick II., became a convert to the church of Rome, and between 1776 and 1784 received over £3,000,000 by hiring his soldiers to the English government to fight against the Americans in the war of independence.

He died in 1785, and was succeeded by his son William IX., who after 1803, when he was raised to the rank of an elector, reigned under the name of William I. Although recognized by Napoleon as one of the neutral princes in 1806, he was expelled from his possessions after the battle of Jena, and Hesse-Cassel was incorporated with the kingdom of Westphalia. On his return to power in 1813, he restored the old order of things. He is identified with the rise of the Rothschilds, and was the father of the Austrian general Haynau, by his mistress Frau von Lindenthal. He was not popular with his subjects. On his death in 1821 he was succeeded by his son, the elector William II., whose relations with his subjects became seriously complicated by his connection with the obnoxious countess of Keichenbach. Riots broke out in 1830. The countess left Cassel, and on Jan. 9, 1831, the elector promulgated the long promised liberal constitution. On the return of the countess fresh disturbances arose, which incensed the elector to such an extent that he also left Cassel. On his death in 1847 he was succeeded by his son, who had officiated as regent after his departure from Cassel, and who assumed the sovereignty under the name of Frederick William I. (born Aug. 20, 1802). Yielding in 1848 to the revolutionary demand for political reforms, but retracing his steps after the reaction had set in, he gave great dissatisfaction to the people, especially in 1850, when the unpopular minister Hassen-pflug came into power as premier, and Haynau, a nephew of the Austrian general, as minister of war.

So great became the excitement that the elector fled, and Hassenptlug saw no other means of saving the crown than by invoking the aid of the other German powers. By their interference quiet was restored, and by their negotiation a new constitution was promulgated in 1852, which met with much opposition on account of its illiberality. After protracted agitations on the subject, a proposal in favor of the reestablishment of the old constitution was presented to the electors by a vote of the second chamber in November, 1859. During the war excitement in 1859, the chambers unanimously voted to join the Austrians against Napoleon III. On May 30, 1860, the government, in accordance with a resolution of the federal diet and with the wishes expressed by the first chamber, promulgated the constitution of 1852, with the amendments adopted in 1857 and with a new electoral law. The new second chamber protested against the constitutionality of the new electoral law and the validity of the new constitution, and on June 21, 1862, the federal diet, on motion of Prussia and Austria, enjoined upon the government of Hesse-Cassel the reintroduction of the liberal constitution of 1831 and the old electoral law of 1849. The government of Hesse-Cassel at first seemed disposed to refuse; but when Prussia mobilized an army corps, it submitted.

Still the quarrels between the government and the legislature continued without interruption. At the outbreak of the war of 1866, the government of Hesse-Cassel sided with Austria, while the diet demanded that the electorate should remain neutral. Immediately after the declaration of war, in June, the Prussians took possession of the country; and when the elector refused to join the new confederation proposed by Prussia, he was taken as a prisoner to Stettin. A decree of Aug. 17 incorporated the electorate of Hesse-Cassel with the dominions of Prussia. In September, 1868, the ex-elector sent a memorial to all the courts of Europe, in which ho protested against the forcible annexation of his state to Prussia, but without effect. In 1873 the elector formally agreed to the cession of his territory to Prussia, and also renounced his right to the revenues of the electorate, the Prussian government granting him as compensation 2,000,000 thalers annually. - Histories of Hesse-Cassel have been written by Rommel (10 vols., 1828-'58), Wippermann (1850), and Roth (1855). (See Hesse, and Hesse-Nassau.)