Answer :
The United States Census Bureau showed in 1890 that C: the American frontier could no longer be distinguished from settled areas.
Why was this the case?
After decades of people moving to the frontier and settling there, several towns and cities as well as states were formed.
As a result, the U.S. Census Bureau noted in its report that the frontier had become quite developed and was much like other settled areas.
In conclusion, option C is correct.
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