In the Wilmette Park District v. Campbell case of 1949, the U.S Supreme Court ruled in favor of Wilmette Park District. The issue at hand was whether or not a park district could be considered a political subdivision of a state and therefore exempt from federal income tax under Section 101(6) of the Internal Revenue Code. The court held that since Illinois law granted park districts substantial governmental powers including eminent domain, taxation, and police power; they were indeed political subdivisions and thus entitled to exemption from federal income tax. This decision clarified an important aspect regarding what entities qualify as "political subdivisions" for purposes of federal taxation.

The dissenting opinion in the case of Wilmette Park District v. Campbell, Collector of Internal Revenue argued that the majority's decision to exempt a municipal corporation from federal taxation was incorrect. The dissenters believed that Congress did not intend for such entities to be tax-exempt under Section 811(c)(2) of the Internal Revenue Code because they are not "corporations organized for exclusively charitable purposes." They pointed out that while these organizations may provide services beneficial to their communities, this does not necessarily make them charitable institutions as defined by law. Furthermore, they contended that granting such an exemption could lead to significant revenue loss and potential abuse if other similar entities sought tax-exempt status based on this precedent.