Two New England Latecomers
The northeastern region of the United States known as New England contains six states. Four of them - Massachusetts, Connecticut, Rhode Island, and New Hampshire - were among the original 13 colonies that became the first U.S. states. The other two, Vermont and Maine, were not. They joined the country later.
Vermont: Once Its Own Republic
Vermont has an unusual story. In the years around American independence, the land that is now Vermont was claimed by neighbouring colonies, especially New York and New Hampshire. Rather than belong to either, Vermont declared itself an independent republic and governed itself for over a decade. It finally joined the United States in 1791, becoming the 14th state - the first new state added after the original 13.
Maine: Once Part of Massachusetts
Maines path was different. For a long time, the territory of Maine was not a separate place at all - it was simply part of the state of Massachusetts, even though the two were not even physically connected. Over time, the people of Maine pushed to govern themselves. Maine finally separated from Massachusetts and became its own state in 1820.
Source
This article was written using information from Wikipedia.