What american argued that overseas expansion was a "safety valve" to keep ambitious americans content?

Frederick Jackson Turner :)

answer; andrew jackson approved nullification by signing it into law,and john calhoun opposed it saying it was unconstitutional;

was a long, primarily nonviolent series of events to bring full civil rights and equality under the law to all americans. the era has had a lasting impact on united states society, in its tactics, the increased social and legal acceptance of civil rights, and in its exposure of the prevalence and cost of racism. in the south violence and fraud in southern elections from 1868 to 1876, which had reduced black voter turnout and enabled southern white democrats to regain power in state legislatures across the south