Columbia subject headings:
Chicago (Ill.)--Commerce.
Harbors--Illinois--Chicago.
Middle West--Commerce.
Railroads--Freight--Rates--United States.
Harvard subject headings:
Chicago (Ill.)--Commerce.
Harbors--Illinois--Chicago.
Middle West--Commerce.
Railroads--Freight--Rates--United States
Princeton subject headings:
Chicago (Ill.)--Commerce.
Chicago (Ill.)--Harbor.
Middle West--Commerce.
Railroads--Freight--Rates--United States.