According to The National Institute of Standards and Technology (NIST): "The United States is now the only industrialized country in the world that does not use the metric system as its predominant system of measurement." And yet, the United States has a history of using the metric system going back to the 1800s. In 1875, the U.S.A. was one of the original seventeen nations to sign The Treaty of the Meter.
In 1960, the metric system was updated by the governing body, General Conference of Weights and Measures, and named Le Système International d'Unités or the International System of Units, abbreviated SI. In 1968, a three year study was authorized by Congress and conducted by the Commerce Department. This resulted in the report A Metric America A Decision Whose Time Has Come. Congress passed the Metric Conversion Act of 1975. While the act encouraged the use of the metric system, it did not mandate it. U.S. adoption of the metric system slowed down. The Omnibus Trade and Competitiveness Act of 1988 (Public Law 100-418) mandated federal agencies to use the metric system when conducting business, by 1992.
So, during the 1970s there was a push to teach and encourage use of the metric system. School curricula stressed the metric system in math and science. (The author of this entry remembers pages and pages of worksheets converting measurements to the metric system and tests where students were required to memorize the formulas). The Metric Cube was one of the many ways of encouraging use of the metric system.
An Italian immigrant, Brumidi combined old-world skills and American subjects to cover the capital building with beautiful frescos. You may not be able to go to DC for a tour, but you can check out this book!