Short answers, pulled from the story.
The French National Assembly declared the metre to be one ten-millionth of the distance from the equator to the North Pole in 1791. This decision established the metre as a geometric construct based on the Earth's meridian arc from Dunkirk to Barcelona.
The original platinum bar known as the Mètre des Archives was created in 1799 and stored in the French National Archives. This prototype was slightly shorter than the theoretical definition because the Earth is not a perfect sphere and the survey contained small errors.
The General Conference on Weights and Measures redefined the metre in 1983 to be the length of the path travelled by light in vacuum during a time interval of 1/299,792,458 of a second. This change fixed the speed of light at exactly 299,792,458 metres per second.
The United States National Institute of Standards and Technology adopted the spelling meter in 2008 to align with American English conventions and the United States Government Printing Office Style Manual. This divergence stems from the Metric Conversion Act of 1975 which gave the Secretary of Commerce authority to interpret the SI for use in the United States.
The ancient Egyptian cubit measured approximately 0.5 metres and was a standard unit used in the construction of the pyramids and other monumental structures. This historical unit was based on the human body and varied from region to region before the modern metric system.