In this chapter, Zinn focuses on the idea that both state and federal government always took the side of the rich employers and land owners over the workers and renters. He does not talk much about monopolies per se. Instead, he is talking more generally about pro-business actions.
What Zinn says is that the governments helped businesses keep control of workers (and to some extent helped them have monopolistic powers) through laws that were passed in response to bribes. He says, for example, that
State legislatures gave charters to corporations giving them legal rights to conduct business, raise money...
He talks about how firms were willing to bribe legislators to get favorable legislation and he talks about how this led to them having excessive market shares. For example, he says
By 1850, fifteen Boston families called the "Associates" controlled 20 percent of the cotton spindleage in the United States, 39 percent of insurance capital in Massachusetts, 40 percent of banking resources in Boston.
However, he does not really specify what actions by the governments are supposed to have made this possible.
Overall, Zinn is trying to make the point that class conflict was important in antebellum America. As part of this, he does mention monopolies to some extent, but that is not the focus of the chapter.
Zinn writes of the Industrial Revolution, "the government of the United States was behaving almost exactly as Karl Marx described a capitalist state: pretending neutrality to maintain order, but serving the interests of the rich." Before the Civil War, as described in Chapter 10, the government intervened to put down working-class revolutions. The two-party system at the state and federal level prevented change, as both parties were similar and in favor of business. For example, during the anti-rent movement in upstate New York in the 1840s, the governor sent in troops to put down the rebellion. Instead, the working class realized that they had to achieve gains by voting, and they were then part of the system, "leaving the basic system of rich and poor intact." When the Dorr Rebellion threatened to disrupt order in Rhode Island, the state militia put it down and instituted reforms that privileged voters from agrarian areas who had paid poll taxes. In addition, state governments allowed monopolies to be created to control risk, and state governments gave charters to these new businesses, spurring the growth of monopolies.
This trend continued after the Civil War. Zinn writes of the election of Grover Cleveland in 1884 over James Blaine that the election was "concealing the basic similarity of the parties by dwelling on personalities, gossip, trivialities." Once Cleveland was elected, the press engaged in reporting on whether he had an illegitimate child rather than on concentrating on real issues.
Reforms were used to pacify the public and avoid deep reform. For example, the Interstate Commerce Commission, intended to prevent railroad abuses, was used so that people did not agitate for deeper reforms (while the act provided limited reform). The Supreme Court, for its part, decided to use the Sherman Anti-Trust Act against labor unions rather than businesses. In addition, the Supreme Court ruled that the 14th Amendment could be used not to protect the rights of African-Americans but as a way to protect corporations. When, in 1877, the Supreme Court ruled in Munn v. Illinois that state laws could regulate the prices a corporation charged farmers to use grain elevators, the American Bar Association launched a campaign in favor of trusts as a way to defeat "communistic" forces. Their campaign succeeded, and the Supreme Court began to rule against state laws regulating corporations. The court decided that corporations were "persons" and therefore were protected under the due process clause of the 14th Amendment.