http://en.wikipedia.org/wiki/Metric_Conversion_Act

From Wikipedia,

Metric Conversion Act
Full title An Act to declare a national policy of coordinating the increasing use of the metric system in the United States, and to establish a United States Metric Board to coordinate the voluntary conversion to the metric system

The Metric Conversion Act is an Act of Congress that then–U.S. President Gerald Ford signed into law on December 23, 1975. It declared the Metric system "the preferred system of weights and measures for United States trade and commerce", but permitted the use of United States customary units in non-business activities. The Act also established the United States Metric Board with representatives from scientific, technical, and educational institutions, as well as state and local governments to plan, coordinate, and educate the American people for the Metrication of the United States.