Great Lakes passenger steamers the lakes grew in size and number, and additional decks were built on the superstructure to allow more capacity. This inexpensive method of adding capacity was adapted from river steamboats and successfully applied to lake-going craft. The Erie Canal opened in 1825, allowing settlers from New England and New York to reach Michigan by water through Albany and Buffalo. This route opening and the incorporation of Chicago in 1837, increased Great Lakes steamboat traffic from Detroit through the straits of Mackinaw to Chicago. The screw propeller was introduced to the Great Lakes by "Vandalia" in 1842 and allowed the building
Great Lakes shipping from January to March. Some icebreakers ply the lakes, keeping the shipping lanes open through other periods of ice on the lakes. The Great Lakes are also connected by the Chicago Sanitary and Ship Canal to the Gulf of Mexico by way of the Illinois River (from the Chicago River) and the Mississippi River. An alternate track is via the Illinois River (from Chicago), to the Mississippi, up the Ohio, and then through the Tennessee–Tombigbee Waterway (a combination of a series of rivers and lakes and canals), to Mobile Bay and the Gulf of Mexico. Commercial tug-and-barge traffic on