Monmouth, battle of, in the American Revolution, fought June 28, 1778, near the village of Monmouth Courthouse (now Freehold, N.J.). Gen. George Washington chose this location to attack the British troops, who were retreating from Philadelphia to New York City. Gen. Charles Lee launched the assault but without warning ordered a retreat. The British, under Sir Henry Clinton, immediately counterattacked, and only the arrival of Washington and Baron von Steuben prevented an American rout. Steuben re-formed Lee's disordered troops and led them back to battle, but the British forces escaped during the night. Lee was later court-martialed and suspended from command for disobeying orders. The legend of Molly Pitcher grew from this battle.

Monmouth, James Scott, duke of, 1649-85, pretender to the English throne; illegitimate son of Charles II of England by Lucy Walter. After his mother's death, he was cared for by Lord Crofts, by whose name the boy was known. In 1662, James went to live at Charles's court. Charles acknowledged him as his son, created him (1663) duke of Monmouth, and married him to Anne Scott, countess of Buccleuch, whose name James now adopted. He held military commands on the Continent (1672-74), became captain general in 1678, and defeated the Scottish Covenanters at Bothwell Bridge in 1679. Politically he became very important after feeling against the succession of the Roman Catholic duke of York (later James II) was heightened at the time of the Popish Plot agitation in 1678. The 1st earl of Shaftesbury and other supporters of a Protestant succession championed Monmouth as heir to Charles and tried in vain to get Charles to prove his son legitimate. In 1679, Charles sent both Monmouth and the duke of York into exile. When Monmouth returned without the king's permission, he was forbidden to come to court but was received enthusiastically in London and the western counties. Monmouth worked with Shaftesbury and the Whig party for the exclusion of James from the succession, and after the arrest of Shaftesbury for treason in 1681 he was heard to speak openly of rebellion. When the Rye House Plot was discovered (1683) and some of the Whig leaders were arrested, Monmouth fled to Holland. James II succeeded Charles in Feb., 1685. In June, Monmouth landed at Lyme Regis, Dorset, and raised a small force. At Taunton he was proclaimed king, and for a short time his chances for success looked very promising. But the gentry failed to come to his support, and his army was routed at Sedgemoor by James's troops, led by John Churchill (later duke of Marlborough). Monmouth was captured and beheaded in London on July 15.

Monmouth, Welsh Trefynwy, town (1981 pop. 7,379), Monmouthshire, SE Wales, at the junction of the Monnow and Wye rivers. The town is a popular tourist and agricultural center with flourishing cattle and produce markets. Industries include food processing and paper manufacture. Fishing is also an activity. Remains of a 12th-century castle (in which Henry V was born), a Norman church, and an old bridge (1272) over the Monnow are there. Monmouth School for boys was founded in 1614. A local museum commemorates Admiral Horatio Nelson's numerous connections with the town.

Monmouth, city (1990 pop. 9,489), seat of Warren co., W Ill.; inc. 1852. Located in a farm area, it is a trade center with a packing plant. Manufactures include pottery, farm tools, and feed. Monmouth College is in the city. Wyatt Earp was born there.

Geoffrey of Monmouth, c.1100-1154, English author. He was probably born at Monmouth and was of either Breton or Welsh descent. In 1152 he was named bishop of St. Asaph in Wales. His Historia regum Britanniae (written c.1135), supposedly a chronicle of the kings of Britain, is one of the chief sources of the Arthurian legend. Geoffrey was the first to write a coherent account of Arthur, establishing the great warrior as a national hero, the conqueror of Western Europe. He drew information from the writings of Bede, Gildas, Nennius, the Welsh chronicles, and folklore, and imaginatively wove the whole into a fictional narrative in the form of a history. His work had great influence on Wace, Layamon, and many chroniclers of the Middle Ages. Another work attributed to him, the Vita Merlini (1148), also influenced later stories of Arthur and Merlin.

(died 1155) Medieval British chronicler. He was probably an Oxford cleric for most of his life. His mostly fictional History of the Kings of Britain (circa 1135–39) traced the descent of British princes from the Trojans; it brought the figure of Arthur (see Arthurian legend) into European literature and introduced the enchanter Merlin, whose story Geoffrey related in the Vita Merlini (circa 1148–51?). Though denounced from the first by other historians, the History was one of the most popular books of the Middle Ages and had an enormous influence on later chroniclers.

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