This question is impossible to answer because no time period is given.
Which nation.
There is no limit. They can have as many states as they desire.
Declaration of Independence
No
The Constitution of the United States of America defines the US as a nation.
In any civilized nation other than the United States.
The four states that allowed slavery was Missouri,Kentucky,Maryland,Delaware and that is from my The American Journey-Building A Nation
There were 16 free states
The United States is one nation of many that exist on earth.
50 States, Washington DC.
The Confederacy was not a state. It was a group of states that declared themselves as a nation separate from the United States. The states that joined it were slave states.
True