Answer:
other great leaders throughout American history
Step-by-step explanation:
When Kennedy says "those who came before us" he is referring to great American leaders inserted in the most diverse branches of industry, politics and science. Kennedy claims that it was these great leaders who allowed the United States to receive a wave of industrialization that promoted the country's advance and it was the duty of future leaders and Americans in general, not to allow these advances to go back, but to go even further.