History of the Metric System
The French are widely credited with the originating the metric system of measurement. The French government officially adopted the system in 1795, but only after more than a century of sometimes contentious bickering over its value and suspicion surrounding the intent of metric proponents.
Gabriel Mouton, a church vicar in Lyons, France, is considered by many to be the founding father of the metric system. In 1670, Mouton proposed a decimal system of measurement that French scientists would spend years further refining.
In 1790, the national assembly of France called for an invariable standard of weights and measurements having as its basis a unit of length based on the Earth's circumference. As a convenience the system would be decimal based, with larger and smaller multiples of each unit arrived at by dividing and multiplying by 10 and its powers.
Borrowing from the Greek word "metron," or "a measure," a commission assigned by the academy gave the name "meter" to the unit of length. The standard it represented was to be constructed so as to equal a fraction of the distance from the North Pole to the equator. Indicative of the difficulties surround adoption of the new system, a survey team charged with measuring the arc of the earth aroused such suspicion that they were harassed and even jailed by local officials as they went about their work. Napoleon himself would even ban the system before it was officially adopted by the French government.
Because of the metric system's adaptability to scientific and engineering work, adoption of the system flourished with rapid expansion of the industrialized world. The U.S. Congress declared the system lawful in commerce throughout the nation in 1866. Twenty years earlier, the French made use of the system compulsory.
In the period of 1970 to 1980, there was a strong movement in the United States toward widespread use of the metric system. That initiative lost momentum, and the nation continues to use a dual system of measurement even though the system is now employed widely throughout the world. There is a strong likelihood that the United States will eventually yield to international pressure to produce and label U.S. goods in metric units. Some industries in the national have already converted to the metric system, which is now known as the SI, or International System of Units.

*"Timeline of Important Dates In The History Of The Metric System
 1670: Gabriel Mouton proposed his decimal system of measurement based on a fraction of the Earth's circumference.
 1671: Jean Picard proposed the swinging pendulum as a measure of length.
 1790: The National Assembly of France asked the French Academy of Sciences to create a standard system of weights and measures.
 1795: France adopted the metric system.
 1840: French government required all Frenchmen to convert to the metric system.
 1866: Congress legalized the use of the metric system in the United States. However, its use was not required.
 1875: The Treaty of the Meter was signed at the close of the International Bureau of Weights and Measures conference.
 1957: The U.S. Army and Marine Corps adopted the metric system. Used as the basis for their weapons and equipment.
 1965: Great Britain began adopting the metric system.
 1988: Congress passed the Omnibus Trade and Competitiveness Act. This act called for all federal government agencies to use the metric system for business by the end of 1992. "
** "Benefits Of The Metric System
One group of units used to measure items such as length, temperature, time and weight is known as the metric system. Some units that come from the metric system you may have heard of : the meter, the kilogram, the second and the kelvin.
For many years, there have been debates about the pros and cons of the metric system. No matter how many arguments or lengthy discussions stem from this debate of meter vs. foot, kilometer vs. mile and kilograms vs. pounds, there are many benefits of the metric system. Here are just a few:

1. The metric system has been adopted by most major countries around the world. By the mid1970s, most countries had converted to the metric system or had plans to do so. When it comes to measurement, the United States is the only major country who has not adopted the metric system! Using the metric system just makes sense, in order to standardize measurement around the globe.

2. The metric system was created by scientists. When invented, it was designed to fit their needs, so it is a logical and exact system.
 3. The metric system was designed to be simple! When making measurements of all kinds, it is only necessary to know a few metric units! In all, there are only 7 base units in this system of measurement! Compared to the twenty base units found in the inchpound system of measurement, it is much easier to remember. The metric system also follows the decimal number system, so each metric unit increases or decreases in size by 10. (Ex. 1 meter = 10 decimeters; 1 decimeter = 10 centimeters; etc.) "
* Source: : http://www.metricmetric.com/metrichistory.html
** Source: http://www.metricmetric.com/benefits.html