Nashville, Chattanooga and St. Louis Railway v. Alabama was a Supreme Court case that was decided in 1904. The case involved a dispute between the Nashville, Chattanooga and St. Louis Railway (NC&StL) and the state of Alabama over the taxation of the railway's property. The NC&StL argued that the state of Alabama had imposed an unconstitutional tax on its property, and that the tax was in violation of the Fourteenth Amendment's Equal Protection Clause. The Supreme Court ultimately sided with the NC&StL, ruling that the tax was unconstitutional and that the state of Alabama had violated the Equal Protection Clause. The Court held that the tax was discriminatory and that it violated the Fourteenth Amendment's guarantee of equal protection under the law. The Court also held that the tax was not a valid exercise of the state's power to tax, as it was not based on any rational basis. The decision in this case established the principle that states must provide equal protection under the law when it comes to taxation.

In the dissenting opinion of Nashville, Chattanooga and St. Louis Railway v Alabama, Justice Harlan argued that the state's taxation of a railroad was unconstitutional under the Fourteenth Amendment because it violated both its Equal Protection Clause and Privileges or Immunities Clause. He believed that by taxing only one type of business in this manner, Alabama had created an unequal burden on interstate commerce which could not be justified as necessary for public safety or welfare. Furthermore, he argued that such a tax would interfere with Congress' power to regulate interstate commerce since it would create an incentive for railroads to avoid doing business in certain states due to their high taxes. Finally, he contended that if allowed to stand this decision would set a dangerous precedent whereby any state could impose discriminatory taxes on businesses operating within its borders without regard for federal law or constitutional protections against discrimination.