Historically the use of the MKS system of units succeeded the centimetre–gram–second system of units (CGS) in commerce and engineering, (1889). The metre and kilogram system served as the basis for the development of the International System of Units, which now serves as the international standard. Because of this, the standards of the CGS system were gradually replaced with metric standards incorporated from the MKS system. The exact list of units used in the MKS system changed over time. It incorporated base units other than the metre, kilogram, and second in addition to derived units. An incomplete list of the base and derived units appears below. Since the MKS system of units never had a governing body to rule on a standard definition, the list of units depended on different conventions at different times.
In 1901, Giovanni Giorgi proposed to the Associazione elettrotecnica italiana (AEI) that this system, extended with a fourth unit to be taken from the units of electromagnetism, be used as an international system. This system was strongly promoted by electrical engineer George A. Campbell .