A history of the measurement of time. From The National Institute of Standards and Technology (an agency of the Technology Administration
U.S. Department of Commerce).
The U.S. Metric Association (USMA), with headquarters in Northridge CA, is a national non-profit
organization, founded in 1916, which advocates U.S. conversion to the International System of
Units (SI), also called the modern metric system.
Includes a chronology of the implementation of the metric system:A chronology of the SI metric system.