Final answer:
The Eisenhower administration focused government spending on modernizing the national highway system, resulting in extensive interstate highways that supported economic growth and national defense.
Step-by-step explanation:
The Eisenhower administration used government spending in modernizing the national highway system. This initiative, known as the Federal-Aid Highway Act of 1956, was one of the most significant domestic programs of Eisenhower's presidency. It created an extensive network of interstate highways that facilitated commerce and travel, fueling economic growth and suburban expansion. The construction of this highway system was seen as vital not only for civilian purposes but also for national defense, as it would enable rapid movement of military forces across the country if necessary.