The critical social legislation passed in 1965 to enhance healthcare access in the U.S. was Medicare and Medicaid. Medicare provides health coverage for individuals aged 65 and older, while Medicaid assists low-income individuals and families with healthcare costs. This landmark legislation aimed to reduce the financial barriers to health access, ensuring that more Americans could receive necessary medical care. The introduction of these programs marked a significant expansion of the federal government's role in healthcare and led to further discussions and reforms surrounding healthcare accessibility and costs in the United States.