1895 - the
income tax
This was actually several cases. The Pollock suit challenged the constitutionality of the income tax imposed by the
Wilson-Gorman Tariff in 1894.
Income taxes had been in use for thirty years, but the Court now found them to be a violation of the Constitution, which requires direct taxes to be apportioned by population. The Court decided that a tax on rental income and a tax on personal property were both direct taxes.
The Sixteenth Amendment negated this decision and specifically permitted income taxes.