Mowry v. Whitney was a United States Supreme Court case that dealt with the issue of whether a state could constitutionally require a person to pay a tax on the transfer of real estate. The case was brought by the plaintiff, William Mowry, who was a resident of Rhode Island. Mowry had purchased a piece of real estate in the state and was required to pay a tax on the transfer of the property. Mowry argued that the tax was unconstitutional because it violated the Fourteenth Amendment's Equal Protection Clause. The Supreme Court held that the tax was constitutional. The Court reasoned that the tax was a valid exercise of the state's police power and that it did not violate the Equal Protection Clause. The Court noted that the tax was applied uniformly to all transfers of real estate and that it was not discriminatory in any way. The Court also noted that the tax was not excessive and that it was necessary to raise revenue for the state. In conclusion, the Supreme Court held that the tax was constitutional and that it did not violate the Equal Protection Clause of the Fourteenth Amendment. The Court noted that the tax was applied uniformly and that it was necessary to raise revenue for the state.

In Mowry v. Whitney, the Supreme Court was tasked with deciding whether a state court had jurisdiction to hear an appeal from a probate court in another state. The majority opinion held that it did not have such authority, as the Constitution does not grant any power to states over those of other states. However, Justice Field dissented from this ruling and argued that while there is no express provision granting such authority, it should be implied by necessary implication due to its importance for interstate commerce and relations between citizens of different states. He further noted that if Congress has failed to provide legislation on this matter then the courts must step in and fill the void left by their inaction. In conclusion he stated that “the interests of justice require” allowing appeals between two or more states when they are related matters concerning property rights or estates located across multiple jurisdictions.