Thirteen Colonies. The Thirteen Colonies, as of 1775, were British colonies on the east coast of North America which had been founded between 1607 (Virginia) and 1732 (Georgia), stretching from New England to the northern border of the Floridas (British East and West Florida).t the time of the war Britain had seven other colonies on the Atlantic coast of North America: Newfoundland, Rupert's Land (the area around the Hudson Bay), Nova Scotia, Prince Edward Island, East Florida, West Florida, and the Province of Quebec.