Northern landmass formed 200 million years ago by the splitting of the single world continent Pangaea. (The southern landmass was Gondwanaland.) It consisted of what was to become North America, Greenland, Europe, and Asia, and is believed to have broken up about 100 million years ago with the separation of North America from Europe.
The number of stripes changed frequently until around 1800. Red, white, and blue became the colours of liberty and an inspiration for other revolutionary flags around the world. Effective date: 19 February 1937.