The original 13 colonies declared independence in 1776 to form the United States of America. The first states of the Union were:

  1. Massachusetts
  2. Connecticut
  3. New York
  4. New Jersey
  5. New Hampshire
  6. Pennsylvania
  7. Delaware
  8. Maryland
  9. Virginia
  10. North Carolina
  11. South Carolina
  12. Georgia
  13. Rhode Island

In 1777 the states were fighting with the English in the Revolutionary War. It was not a good time for the Continental Congress to let the state of Vermont into the Union, though the people of Vermont were longing to join the US. All the states of the Union found this decision optimal. Anyway, on the 15th of January, 1777, Vermont gained independence, but governed itself until 1791. The negotiations of 1790 resulted in the decision to take $30,000 from Vermont to let it join the United States. Even if this amount of money was considered enormous in those times, both sides accepted the decision.

On the 4th of March, 1791 Vermont officially joined the United States of America. It is still often referred to as the 14th state and the first state to enter the Union after the Revolution.

More Info: en.wikipedia.org