The Magoun v. Illinois Trust and Savings Bank case in 1897 revolved around the constitutionality of a progressive inheritance tax law in Illinois. The plaintiff, George F. Magoun, was an executor of an estate who argued that this law violated the Equal Protection Clause of the Fourteenth Amendment because it taxed inheritances at different rates based on their size - larger estates were taxed more heavily than smaller ones. However, the U.S Supreme Court upheld the validity of this progressive taxation system by a majority decision. They ruled that such laws did not violate any constitutional rights or protections as they were within a state's power to levy taxes as they saw fit for public purposes and welfare.

In the dissenting opinion for Magoun v. Illinois Trust and Savings Bank, Justice Harlan argued that the tax imposed by Illinois on gifts made within two years of death was unconstitutional. He contended that it violated both due process and equal protection under the Fourteenth Amendment because it arbitrarily distinguished between different types of property transfers without a rational basis. Furthermore, he believed this law to be an unlawful attempt to evade constitutional limitations on estate taxes by disguising them as gift taxes instead. In his view, such a tax could not be justified simply as a means of preventing evasion of estate duties; if allowed to stand, it would set a dangerous precedent allowing states to impose arbitrary and discriminatory taxes in other contexts too.