Alton, a city and port of entry of Madison county, 111., on the left bank of the Mississippi river, 3 m. above the mouth of the Missouri, about 20 m. below the mouth of the Illinois, and 25 m. N. of St. Louis, Mo.; pop. in 18(50, 6,332; in 1870, 8,865. Its length along the river is about 2 2/3 m.; its average breadth about 1 1/3 m. A little W. of the centre it is divided by a small stream called Piasa creek, which has its sources in springs within and near the city limits, and is arched over and used as a main sewer. The valley of this stream and the bottom land W. of its mouth along the Mississippi are the chief seats of business. Each side of this valley and up and down the river from it the ground rises rapidly and in some parts abruptly into irregular and broken bluffs, the highest being 224 1/2 feet above the river. The whole city is underlaid with limestone rock, which is full of fissures and caves, crops out in many places, and in the western part along the river forms perpendicular bluffs. Alton is the centre of a rich farming country. Besides the river navigation, three railroads connect it with all parts of the country.

The principal manufacturing establishments (1872) are two large flouring mills, two iron founderies, an extensive woollen mill, glass works, a castor oil mill, a large tobacco manufactory, a manufactory of agricultural implements, a planing mill, and several lumber yards and steam saw mills. The packing business is carried on, but less extensively than formerly. Lime of excellent quality is made, and, with building stone, is exported largely. There are two banking houses, gas works, and a steam ferry to the opposite shore. There is a large Roman Catholic cathedral, Alton having been made a bishopric in 1868. The other churehes'are: one Baptist, one orthodox Congregational, one Unitarian, two Protestant German, one Presbyterian, one Cumberland Presbyterian, one Methodist, one Catholic, and one colored Baptist. Alton has a daily and weekly newspaper, a weekly paper in German, and a weekly religious journal, the " Cumberland Presbyterian," the organ of that denomination in the West. There are several benevolent societies and a library association. The state penitentiary, established here in 1827, was removed several years since to Joliet. The buildings are yet standing, and were used during the civil war as a government prison. Upper Alton, about 1 1/2 m.

E., is the seat of Shurtleff college, a Baptist institution. (See Shuetleff College.) In 1807 there was one small building where Alton now stands, used by the French of Cahokia and St. Louis as a trading house with the Indians. The town was laid out in 1817.