Explain the difference between an open frontier and a closed frontier

It is undeveloped region that is open to settlement; open border.It means the land or territory that forms the furthest extent of a country's settled or inhabited regions. Often frontiers. the limit of knowledge or the most advanced achievement in a particular field: the frontiers of physics.

In 1890, the Census Bureau broadcast the closure of the frontier, meaning that in the west there was no apparent tracts of land without settlers. This news was a distinguished event in American history; the frontier represented danger because of the Natives who lived in the region but also freedom and opportunity.

eroupe is a great mideval place and alot of wars went on alao

b) the confederacy had to pay all union war expenses.