Question

In 1890, the U.S. Census Bureau said there was no more frontier. How did
that realization affect the way in which Americans viewed their natural
resources?

Answer 1

One way in which this  realization affected the way in which Americans viewed their natural resources was that they now saw them as "limited"--in that Americans began looking to other areas--specifically in the Pacific and Asia--that they could dominate in order to extract resources.