Lyndon B. Johnson is best known for which of the following achievements?

Lyndon B. Johnson is best recognized for establishing the Medicare and Medicaid systems, which were landmark programs in American social welfare. Under his administration, particularly during the Great Society initiatives in the 1960s, Johnson aimed to address poverty and improve healthcare access in the United States. Medicare, initiated in 1965, was designed to provide health coverage to the elderly, while Medicaid, also launched in the same year, aimed to assist those with low income. These programs have had a lasting impact on the American healthcare system, ensuring that millions of Americans have access to necessary medical services.

While Johnson played a significant role in civil rights legislation and contributed to the Vietnam War efforts, he is most directly associated with the establishment of these healthcare programs, which continue to influence American society today.