CAIRO, a city of the United States, capital of Alex-ander county, Illinois, situated between the Ohio and Mississippi, at the extreme south of the State, 147 miles from St Louis by rail. On account of its low situation it has often suffered from inundations, especially in the summer of 1858, when it was nearly destroyed, but it is now better protected by embankments. Steamers ply between the city and the Ohio and Mississippi ports, and it is an important depot for the produce of the neigh-bouring States. Large warehouses have recently been built, and both city and trade are steadily increasing. Cairo possesses a fine custom-house and county buildings. Population in I860, 2188, and in 1870, 6267.