In 1776, most Americans lived within 15 miles of the Atlantic Ocean. By 1820, about 30% of Americans lived between the Appalachian Mountains and the Mississippi River.
This is an example of ___.

answer: the ocean

explanation: if you map out 30 n and 40 n latitude, you will get the ocean

polisit can also mean a body of citizens. in modern historiography, polis is normally used to indicate the ancient greek city-states, like classical athens and its contemporaries, and thus is often translated as "city-state". the body of citizens came to be the most important meaning of the term polis in ancient greece.