The U.S. Supreme Court case St. Louis-San Francisco Railway Company v. Middlekamp, State Treasurer of the State of Missouri, et al., 1920 revolved around a dispute over taxation on railroad property in Missouri by the state's treasurer and other officials against the railway company. The railway company argued that its properties were being unfairly assessed at higher values than other types of real estate within the state, which resulted in disproportionately high taxes for them compared to others - an alleged violation of their Fourteenth Amendment rights (equal protection under law). However, after examining evidence presented regarding assessment practices and tax rates applied to different classes of property across various counties in Missouri, the court ruled against this claim stating there was no clear proof that discrimination had occurred or that any intentional systematic undervaluation existed outside normal variations due to human error or judgment differences among local assessors.

In the dissenting opinion for St. Louis-San Francisco Railway Company v. Middlekamp, it was argued that the majority's decision to uphold a Missouri tax on intangible property violated both due process and equal protection clauses of the Fourteenth Amendment. The dissenters believed that this taxation unfairly targeted out-of-state corporations while exempting in-state ones from similar taxes, creating an unjustifiable discrimination against interstate commerce. They also contended that such a tax could not be justified as a means of compensating for other taxes avoided by these corporations since there was no evidence to suggest they were evading their fair share of state taxes. Furthermore, they asserted that even if such evasion did occur, it would still not justify imposing an additional burden on them through discriminatory taxation.