Lamaster v. Keeler was a United States Supreme Court case that dealt with the issue of whether a contract between two parties was valid. The case involved a dispute between two parties, Lamaster and Keeler, over a contract for the sale of a tract of land. Lamaster had agreed to purchase the land from Keeler for a certain sum of money, but Keeler refused to accept the payment and instead sought to have the contract declared invalid. The Supreme Court held that the contract was valid and enforceable. The Court found that the contract was supported by consideration, meaning that both parties had given something of value in exchange for the agreement. The Court also found that the contract was not void for lack of consideration, as Keeler had argued. The Court further held that the contract was not void for lack of mutuality of obligation, as Lamaster had argued. The Court's decision in Lamaster v. Keeler established that a contract between two parties is valid and enforceable if it is supported by consideration and does not lack mutuality of obligation. This decision has been cited in numerous subsequent cases and has become an important precedent in contract law.

Justice Field delivered the dissenting opinion in LAMASTER v. KEELER, arguing that the majority had misinterpreted the law and failed to consider relevant evidence. He argued that under California law, a married woman was not allowed to own property independently of her husband; thus, when Mrs. Lamaster purchased land with money she received from her father's estate, it belonged solely to Mr. Lamaster as her husband and legal representative at the time of purchase. Justice Field further noted that while there were some exceptions for separate property held by a wife prior to marriage or acquired through inheritance after marriage, none applied in this case since Mrs Keeler did not have any such rights over the land before or during their marriage. Thus he concluded that Mr Keeler should be able to recover his debt from Mr Lamaster without having recourse against Mrs Lamaster’s separate estate because she never owned an interest in it herself according to California law at the time of purchase