Final answer:
The passage of The National School Lunch Act in 1946 was considered Richard B. Russell's greatest legislative achievement, providing schools with funds to improve child nutrition and forming a foundation for later educational and social welfare initiatives.
Step-by-step explanation:
Richard B. Russell deemed the passage of The National School Lunch Act in 1946 as his greatest accomplishment during his tenure in Congress. This pivotal legislation provided funding to schools for meal programs, aiming to enhance the health and well-being of children across the nation. It set the stage for later expansions in federal support for education and nutrition under President Lyndon Johnson during the 1960s, including the establishment of Medicaid, Medicare, and extensive educational programs such as the Elementary and Secondary Education Act, the Higher Education Act, and Head Start preschool program. These initiatives were part of a larger movement to increase the role of national government in various aspects of society, including education, health, and civil rights.