Expansion of Equal Protection Clause

In the landmark case of Brown v. Board of Education (1954), the Supreme Court ruled that state-sponsored segregation of public schools violated the Equal Protection Clause of the Fourteenth Amendment. The decision was pivotal in overturning the precedent set by Plessy v. Ferguson (1896), which upheld the constitutionality of racial segregation under the "separate but equal" doctrine. Following this ruling, several state legislatures undertook actions to circumvent the Court's decision, leading to subsequent cases that further clarified the application of the Equal Protection Clause. Which of the following subsequent cases most directly expanded the understanding of the Equal Protection Clause regarding gender discrimination?