What was the most important challenge facing the United States between Reconstruction and the End of the Cold War? What was the second most important? Finally, how did those challenges make the United States different in 1990 from how it was in 1880?

What was the most important challenge facing the United States between Reconstruction and the End of the Cold War? What was the second most important? Finally, how did those challenges make the United States different in 1990 from how it was in 1880?