Khorassan, the largest province of Persia, bordering on Afghanistan, contains about 210,000 sq. m., of which nearly one-third is a vast salt waste; of the remainder a large portion consists of plains of shifting sand. The fertile districts are in the north, where the high range of the Elburz crosses the province, throwing out spurs, and forming a mountainous district, abounding with fertile and well-watered valleys. Artificial fertilisation by means of canals was here carried on to a great extent in ancient times, but the incessant disturbances which have unsettled the district for the last thousand years have almost put an end to this system. The chief products are grain, cotton, silk, hemp, tobacco, aromatic and medicinal plants, fruits, wine, salt, gold, silver, and precious stones, especially turquoises, also camels, horses, and asses. The chief towns are Meshed, the capital, Nishapur, Kutchan, Shahrud, Khaf, Kain, and Tebbes.
Khorassan means in ancient Persian eastwards, and is said to have extended over all central Asia in the north, to the Helmund on the S., to the Pamir on the E., and to the Caspian on the W. After the conquest of the Arabs the country beyond the Oxus became a possession of the Samanide dynasty, whilst Kharasm (the modern Khiva) was taken by the Seljuks. Herat and the adjoining districts remained in the possession of the Timurides, though sometimes retaken by the Persians, until finally it fell under the sway of the Afghans. Khorassan, being situated on the highway of the Turko-Tartar inroads into the west of Asia, had always to bear the brunt of predatory hosts coming from beyond the Oxus, and its chief towns repeatedly suffered destruction. Recently the invasion has come from the west; and the northern slopes of the Kubbet Mountains, together with the oasis of Merv, including the middle course of the Heri-rud, have been annexed by Russia. See MacGregor's Narrative of a Journey through Khorassan (1879); and for the 'Veiled Prophet of Khorassan,' see MOKANNA.