Coatzacoalco, Or Goatzaeoalcos, a river of Mexico, rising in the unexplored part of the Sierra Madre, and flowing N. across the isthmus of Tehuantepec into the bay of Coatza-coalco, in the gulf of Mexico, in lat. 18° 8' 30" N., lon. 94° 17' W. It is the most important of the streams which water the N. slope of the isthmus, on account both of its numerous tributaries and its extensive basin, and of its position as a part of a projected channel of in-teroeeanic communication. A commission sent out by the United States in 1850 ascended by small boats to the village of Santa Maria Chi-malapa, 4 1/2, m. below its junction with the Chimalapilla; and in the winter of 1870-'7l it was again explored by a party under command of Capt. R. W. Shufeldt, U. S. N., who demonstrated the practicability of a canal by this route. About 45 m. below Santa Maria it receives the Malatengo on the west, and on the same side, 22 m. further down, it is joined by the Sarabia. The Jumuapa enters 17 m. below, and next to it the Jaltepec, which is the principal tributary on the west, being navigable by canoes 50 m. at all seasons. The Chalchijapa joins on the east, 22 1/2, m. below the Jumuapa. Thence to the point of Horqueta, 40 1/2 m. further, the affluents are all small.

After the junction of the Sarabia the hills become inconsiderable, and below the mouth of the Jaltepec the banks of the river are in few places more than 10 or 15 ft. high, and are often overflowed. The current is scarcely perceptible, and during the dry season shoals are met with having only 18 inches of water over them. At the Horqueta, 102 m. below the Malatengo, the river branches, and after forming the island of Tacamichapa, reunites. The W. branch is called the Mistan, the E. the Apotzongo. The former, which is the longer, is 34 m. long and has an average depth of 13 1/2 ft. The Coa-huapa joins the river on the east, 10 m. below the junction of the branches; 44 m. below its mouth, on the W. bank, is the village of Mina-titlan; and 4 1/2, m. below this the river Us-panapan, the most considerable of the many tributaries of the Coatzacoalco, joins it on the east. From the lower point of the island of Tacamichapa to the mouth of the Coahuapa the depth is 26 1/2 ft., and thence to the bar from 33 to 40 ft. The breadth between the same points is from 130 to 700 yards. It is thus navigable for about 35 m. for the largest ships. At the mouth of the river, which lies 115 m.

W. of the mouth of the Tabasco, and 143 1/2 m. in a direct line from the harbor of Ven-tosa, on the Pacific coast of the isthmus, there is a bar, the soundings over which made by order of Cortes in 1520 gave the same results as those obtained in 1850 and in 1871. It appears to be of limestone rock, with a light covering of coarse sand, and has two passes, one 350 ft. wide and 13 ft. deep, and the other 100 ft. wide and between 11 and 12 ft. deep. The breadth of the stream at its mouth is 1,500 ft. Just within the bar is the little village of Coatzacoalco, which has grown up since 1855, and is now frequented by vessels engaged in the mahogany trade.