In 1840 Chicago had been an unimportant settlement of 4500 persons, but by the opening of the war it had grown to twenty-five times that size, and added 800,000 between 1870 and 1890. It had early become evident that the city was the natural outlet toward the East for the grain trade and the slaughtering and meatpacking industry of the upper Mississippi Valley.
"The United States Since The Civil War"
Charles Ramsdell Lingley
So, if two merchants going down town to their business agree in the street car that they will charge a certain amount for a barrel of flour or a ton of coal that week, this would probably be regarded as reasonable at the common law; but the common law, like these early statutes of England, looked primarily, if not exclusively, to the welfare of the consumer; they always speak of the common weal of the people, or of combinations to the general hurt of the people, and general combinations to fix prices or to limit output are therefore always unlawful; so a combination that only one of them should exercise a certain business at a certain place-like that of our four great meatpacking firms, who are said to have arranged to have the buyer for each one in turn appear in the cattle market, thus being the only buyer that day-would be unlawful, when the restraint of trade resulting from an ordinary purchase would not be.
"Popular Law-making"
Frederic Jesup Stimson