How was The Interior Plains Named the Interior plains?

because they are in the interior region or center of the united states

Coastal plains are very rare on islands, as they are near the ocean. But they are plains on the borders of a country, or on an island, the shore. Interior plains are plains nowhere near the border or...

they are both flat

The Coastal plain is different from an interior plain because a coastal plain lies along the sea coast. Coastal plains also have low relief. The interior plain lies away from the coast and the...

i do not know from ajae