The Des Moines case was a landmark Supreme Court decision in 1871 that established the power of the federal government to regulate the navigable waters of the United States. The case arose when the state of Iowa attempted to impose a tax on vessels navigating the Des Moines River, which was a navigable waterway. The Supreme Court held that the federal government had exclusive authority to regulate navigable waters, and that the state of Iowa could not impose a tax on vessels navigating the Des Moines River. The decision was significant because it established the federal government's power to regulate navigable waters, which has been used to protect the environment and promote commerce. The decision also established the principle of federal supremacy over state laws, which has been used to protect civil rights and other important issues.

In The Des Moines, 1871, the Supreme Court was tasked with determining whether a state law that prohibited public speaking in certain areas violated the First Amendment. In an 8-1 decision, the majority of justices held that it did not violate any constitutional rights because it only regulated conduct and had nothing to do with speech itself. Justice Field dissented from this opinion and argued that while states have broad authority to regulate conduct for public safety purposes, they cannot use such laws as pretexts for suppressing free expression or infringing on citizens' right to freedom of speech. He further argued that if states can pass laws prohibiting people from expressing their views in certain places then those same governments could also prohibit them from doing so anywhere else. As such, he concluded that the law at issue should be struck down as unconstitutional since it infringed upon citizens' fundamental right to freely express themselves without fear of government interference or censorship.