The First Unitarian Society of Chicago v. Faulkner et al. was a case heard by the United States Supreme Court in 1875. The case involved a dispute between the First Unitarian Society of Chicago and the Faulkner family over the ownership of a piece of land in Chicago. The Society had purchased the land in 1867, but the Faulkner family claimed that they had a prior claim to the land. The Society argued that the Faulkner family had no legal right to the land, as they had not paid taxes on it for several years. The Supreme Court ruled in favor of the Society, finding that the Faulkner family had no legal right to the land. The Court held that the Society had acquired the land in good faith and had paid the taxes due on it. The Court also held that the Faulkner family had failed to pay taxes on the land for several years, and thus had no legal right to the land. The Court also noted that the Society had made improvements to the land, and thus had a valid claim to it. The decision of the Supreme Court in this case established the principle that a purchaser of land in good faith and for value has a valid claim to the land, even if the prior owner has failed to pay taxes on it. This principle has been applied in numerous cases since then, and is still an important part of property law today.

In First Unitarian Society of Chicago v. Faulkner et al., the Supreme Court was tasked with determining whether a state law that required religious organizations to pay taxes on property used for non-religious purposes violated the Free Exercise Clause of the First Amendment. The majority opinion held that such taxation did not violate this clause, as it applied equally to all religions and did not single out any particular religion for special treatment. Justice Field dissented from this ruling, arguing that while states have broad powers when it comes to taxation, they cannot use those powers in a way which discriminates against or interferes with religious practices or beliefs. He argued further that since Illinois' tax code specifically exempted churches from paying taxes on their properties if they were used exclusively for religious purposes but imposed them if any part of the property was used for other activities (such as renting out space), then it constituted an unconstitutional discrimination against religion by singling out certain types of church activity and penalizing them through taxation.