When America began as a nation of thirteen states, the "frontier" was the land between the states and what other boundary? California Florida Canada Pacific Ocean Mississippi River Atlantic Ocean

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Explanation:

The United States of America was created on July 4, 1776, with the Declaration of Independence of thirteen British colonies in North America. In the Lee Resolution of July 2, 1776, the colonies resolved that they were free and independent states. The union was formalized in the Articles of Confederation, which came into force on March 1, 1781, after being ratified by all 13 states. Their independence was recognized by Great Britain in the Treaty of Paris of 1783, which concluded the American Revolutionary War. This effectively doubled the size of the colonies, now able to stretch west past the Proclamation Line to the Mississippi River. This land was organized into territories and then states, though there remained some conflict with the sea-to-sea grants claimed by some of the original colonies. In time, these grants were ceded to the federal government.

i believe it is the second one.   if correct plz mark brainliest.