In Chapter 11 of A People's History of the United States, "Robber Barons and Rebels," Zinn's message is that starting in 1877, following Reconstruction, the government helped economic and political elites take control of the nation to create unprecedented economic growth. In the process, the elites and government took advantage of labor, including African-American, Chinese, and white labor. Immigrants in particular struggled while working under harsh conditions.
Zinn writes, for example, about the way in which the Presidents during this time did little to enact reforms to benefit most people, while they put into place policies to help business. In addition, the Supreme Court declared that corporations were "persons" and therefore entitled to protections under the due process clause of the 14th Amendment, while denying this protection to African-Americans. Zinn's message is that the government did and can collude with business interests to further the power of the elites while avoiding reforms to benefit the vast majority of Americans.