_Chicago_, at the head of Lake Michigan, has a very heavy lake-trade. The mouth of Chicago River, the natural harbor of the city, has been improved by a system of basins and breakwaters. The river itself has been converted into a ship and drainage canal that is connected with the Illinois and Mississippi Rivers. It is now an outlet instead of a feeder to the lake, and the city built about old Fort Dearborn has become the greatest railway centre in the world. [Illustration: GENERAL VIEW OF LOCKS AND CANAL, SAULT STE. MARIE] _Milwaukee_ has a situation in many ways resembling that of Chicago, its harbor being the mouth of Milwaukee River. Like Chicago, it owes its importance to its lake-trade. _Detroit_ (with _Windsor_, Ont.) owes its growth partly to its strategic position on the strait connecting Lake Huron and Lake Erie, and partly for its position between the lakes. It is an important collecting and distributing point for lake-freights, and the chief centre of commerce with Canada. Several east-and-west trunk lines and local lines of railway have freight terminals in the city; it is also the centre of the most complete system of interurban electric railways in the world. _Port Huron_ (with _Sarnia_, Ont.) has a geographic position similar to that of Detroit, and is also an important lake-port. The St. Clair River is tunnelled at this point. _Cleveland_, _Toledo_, _Sandusky_, and _Erie_ contribute very largely to the lake-trade. _Grand Rapids_ is the business centre of furniture manufacture of the United States. The great iron-ore ranges about Lake Superior have had much to do with the growth of the local lake-trade. This has resulted in the establishment of a large number of shipping-ports near the head of the lakes, and also a number of receiving ports on the south shores of Lake Erie and Lake Michigan. Some of the latter have become also great manufacturing centres of structural iron and steel. Various centres of industry at a considerable distance from the Great Lakes are contributors to their trade. Thus, on account of the low rate for grain between _Chicago_ and _New York City_--about 5-1/4 cents per bushel--there are yearly very heavy shipments of the grain designed for Liverpool. _St. Paul_ and _Minneapolis_ are also collecting and distributing centres of lake-freights. A considerable part of the business of the lake-region is carried on by the Canadians, who have improved their resources for production and transportation to the utmost. [Illustration: _Copyright, Detroit Photographic Co._ AURORA IRON MINES, IRONWOOD, MICHIGAN] =The Northern Mississippi Valley Region.=--This region extends from the Appalachian ranges to the western limit of wheat and cotton growing. On the south it is limited by the cotton-growing region. Its boundaries are therefore climatic and commercial.