Where was the metre–tonne–second system invented?

I always think it very strange that the French invented a system of weights and measures which includes the kilogram (kg) and the kilometre (km). The French do not really use the letter’k’.

SI units are based on seven quantities which include MKS units (metres, kilograms, second s). The other units are ampere (current), kelvin (temperature), candela (luminous intensity) and mole (amount of substance).

the U.S.A. will never switch to metric!! Too expensive!!