It started out as a monarchy from 753 BC - 509 BC after the last king died Rome turned into a republic all the way from 509 BC - 27 BC and from 27 BC it turned from a republic all the way into a Empire from 27 BC - 476 AD. Long live the Empire!!<span />
To me at least it would be the first answer. if you would like a proper explanation to this let me know :D
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They did it because King George lll hoped to placate Native Americans who had sided against him during the recently concluded Seven Years' War.
Although the overall causes of Shay's Rebellion were somewhat complicated, the most direct factor was "high taxes" since many people didn't believe the federal government should tax consumer goods.