The metric system is the internationally agreed-upon standard of measurement throughout the world. In fact, only three countries have not officially adopted the system: Burma, Liberia and the United States.
The system, which conducts measurements based on units of ten, was introduced by France in 1799. The system was officially approved for use in the United States in 1866, but it was only adopted for scientific and medical purposes, rather than for common use.
In 1927, however, millions of people signed a petition urging Congress to switch to the metric system. The petition, of course, failed.
A more recent petition for the U.S. to adopt the system made it's way to the White House, where the U.S. Department of Commerce's National Institute of Standards and Technology director Patrick D. Gallagher issued a formal response explaining why the country has not yet adopted the system.
