Metric system
In 1975 the Metric Conversion Act started a formal metrication process.  Metrication was to be voluntary. It was to be coordinated by the U.S. Metric Board. In 1988 the Omnibus Trade and Competitiveness Act said that metric units had to be used for all federal projects.  The Act did not apply to state projects. Some states demanded that metric units be used but other states did not. Some industries changed to using metric units but others did not.  Soft drinks are sold in metric quantities. Milk is sold in customary units.  Metric units are widely used in the design of motor cars.  Aircraft such as the Boeing 787 Dreamliner were designed using mainly customary units.