The Metric System is a decimalized unit system used near globally. The United States is the only non-metric industrialized nation. The focus of this chapter is on how the actions of interested parties have effected the adoption. A primer on the global history of the metric system can be found here.
The history of the metric system in the United States can be traced to the Metric Act of 1866, signed by Andrew Johnson, which made legal the use of metric units in commerce. Congressman John Kasson, chairman of the House Committee on Coinage, Weights, and Measures, exemplified the positivity towards the adoption, hoping that "a further act of Congress can fix a date for its exclusive adoption as a legal system".  In 1875, the United States attended the Metric Convention even though the nation had not converted. The U.S. did however, sign the treaty, that created the International Bureau of Weights and Measures to regulate the metric system. On April 5, 1893, T.C. Mendenhall, the Superintendent of Weights and Measures, decided that the metric system would become the standard unit system in the U.S. and since then the American unit system has been defined in terms of the metric system. In 1902, a bill supporting full conversion of the Federal government from U.S. Customary to the metric system was introduced to Congress. The bill lost by a single vote. Early metrication efforts were high-minded, but little came of them.
In 1975 the 94th U.S. Congress passed the The Metric Conversion Act. This bill created the United States Metric Board and initiated planning and preparation for metric system conversion. In 1988, President Reagan signed the Omnibus Foreign Trade and Competitiveness Act. This bill required all federal agencies convert, "to the extent economically possible", to the metric system by the end of the 1992 fiscal year, but disbanded the USMB.  In 1991 President George H.W. Bush signed Executive Order 12770, reiterating this requirement. While some agencies did convert, the executive order stated that if conversion could "cause significant inefficiencies or loss of markets to United States firms," the requirement was waived. Since this time there have been no further requirements for federal agencies or other groups to convert to the metric system.
Recently, there have even been some political movements away from the metric system. In 2004, the California Department of Transportation initiated movements back to the customary system. In a letter to the department, acting chief engineer Mike Leonardo establishes a "Metric to English Transition Team" to help. He cites a benefits of aligning with commercial partners, in addition to 'long-term financial advantages to the department.' 
Proponents of U.S. metrication commonly cite the fact that the United States is the only industrialized country in the world that has not yet converted to the metric system. By converting, it would unify measurement systems around the world and improve efficiency of international trade and commerce. Currently, some industries in the United States do use the metric system. These include the medical industry, sciences, and the military.
The United States Metric Association was created to encourage the voluntary use and conversion to the metric system in the United States.  Created in 1916 as the American Metric Association, the USMA has been educating people about the metric system and advocating for its use. It has worked closely with the United States Metric Board and the U.S. government proposing laws and studying metric system usage.  The USMA attempted to personalize losses caused by unit confusions by publishing "Metric Mixups."  The implicit point of compiling the events is that if there were just one system, such accidents would not occur.
The United States Metric Board was created by the Metric Conversion Act of 1975. Its role was to facilitate the voluntary metric conversion by government agencies and other organizations. By 1981 the USMB had produced TV public service announcements (PSAs) and 27 radio PSAs. These PSAs served to encourage conversion to metric units.
One of the roles of the USMB was to publicize programs and allow interest groups to submit programs and comments on programs. In 1981 the United States Metric Council submitted to the USMB two metric conversion plans for the shipping and billing of industrial chemicals and for instrument charts, scales, and mounting dimensions. The USMB met to discuss each of these plans and voted to approve both. The board passed two resolutions in accordance with these plans and stated in both that, "This endorsement is not a mandate to proceed, since the USMB does not have such powers... The implementation of the plan is now a matter for decision by individual companies, organizations, and persons..."  By passing these resolutions, the board acknowledged beneficial plans, but could do nothing to actually implement the plans.
The American National Metric Council was established by the American National Standards Institute in 1973. It was the view of the council that U.S. metrication was going to be a complex process involving hundreds of different organizations. The council's role was to coordinate conversion efforts in order to ensure that the metric system was applied consistently. The ANMC proposed two metric conversion papers to the USMB in 1981 and both were approved. They also published two newsletters: the Metric Reporter, and Metric Messenger for Consumers. The Metric Reporter included editorials, stories, and updates about the progress of metrication both in the government and private industries. The Metric Messenger for Consumers was written for the general public and included various articles about the metric system and its usage.
The non-mainstream arguments are varied, but usually attempt to vilify the metric system or glorify the English units. There have been attempts to associate the metric system with Dictatorial regimes, and thus shed English units in a more positive light: "Most Americans can remember, from the late 1970s, when U.S. metrication (metric conversion) was proceeding like a five-year plan commanded by the Kremlin." The English units have been associated with being patriotic, which attempts to show opposition to the "American" units as being un-patriotic.
Pop culture media often presents metric conversion as being absurd and presents the topic as a joke, or to be humorous. Grandpa Simpson presents the argument via song that the metric system is something to be opposed, and likens it to the Illuminati or Masons. In the T.V. show The Big Bang Theory the metric system is shown as something that only nerds and scientists care about. Saturday Night Live has presented the base 10 quality as applied to an alphabet, or "Decibet", a play on words originating from a metric prefix.
The two main economic factors associated with US metrication are the cost of conversion and the cost of mistakes.
Given that space flight is an increasingly international enterprise, it has received particular attention regarding its varied use of the metric and customary systems.
Mars Climate OrbiterEdit
An expensive effect of metrication was the loss of NASA's Mars Climate Orbiter. In 1999 NASA launched a probe to Mars, assembled with the assistance of multiple contractors. Upon reaching Mars, it did not enter orbit, but entered the Martian atmosphere where it was destroyed. A single contractor failed to abide by NASA's metric requirement. This contractor used imperial pound-force rather than metric Newtons. The resulting miscalculation of thrust led to the probe's destruction, a $327 million mistake. 
The Constellation Program, a 2010 NASA project for human spaceflight, was granted permission to not be metric-compliant, for which NASA has received criticism. The primary reason for this was the $368 million price tag required for contractors to convert all of the prior work and documentation to metric units. After many years of regular business in U.S. customary units it is more difficult every day to perform the conversion to the metric system.
The Vision for Space Exploration expects astronauts to return to the Moon by 2020 to set up a manned lunar outpost. NASA and 13 other space agencies discussed methods to coordinate their lunar exploration programs. The decision was unanimous to use metric units exclusively so that parts and supplies would be interchangeable between habitats. 
The medical community recognizes the need to switch to the metric system, but remains very dependent on English units. Paramedics calculate dosages completely in metric units, but doctors can prescribe drug dosages in any units they want.  There have been cases where patients have underdosed and overdosed because of unit mix-ups. Overdosed patients have been at risk for seizure, stroke and even death. In underdosed patients the original illness will not be prevented and may further progress.
Gasoline pumps offered a unique chance for metric conversion. Businesses were wary of having to retrofit their pumps to allow for gas prices greater than 99.9¢ per gallon. The USMB found that selling gas by the liter, would save $94 million dollars -- nearly $300 million 2012 dollars. Gas would not have exceeded $1/liter until the mid 2000's.
Citizens of the United States, especially the older generations, have spent lots of time working with English units. Complete conversion to metric units is viewed by these people to be a hassle. This is a case of path dependency. The United States is losing its dominance in world trade. Before, other countries were forced to convert to English units for trading, but now they are forcing the United States to convert to metric. This incentivizes businesses to convert to metric units to keep their trading partners. 
The United States is the only industrialized nation that has not converted to the metric system. Some researchers believe that patriotism is to blame. In a report by Kidela Capital Group, Jane McFadyen writes:
- “The United States breeds an almost unparalleled patriotic fever among its citizens, the likes of which is rarely found outside North Korea, and it is perhaps this strong sense of national pride and hint of superiority that prevents Americans from appearing to be the last to jump on the bandwagon.” 
Patriotism stems from our need to honor our parents by being loyal to their nation. This can almost directly be related to English units; people think that they are honoring their parents by using English units. 
Currently, both the metric and English systems are taught in elementary school. Equal weight is given to both systems in textbooks. Since mostly English units are used by students at home, metric units are taught and then related to their equivalence in English units in school. Researchers believe that dual system usage causes students in the United States to perform poorly in math and science when compared to the rest of the world.  Computers are now reducing the need for fluency in both systems. With the click of a button, units can be converted back and forth. 
We've found that a system of measures is more than an a way to measure things. People have feelings and memories to their use of the customary system. Even its name embodies this link -- it is 'customary,' usual and friendly. Any program whose intent is to convert must take into account this emotional attachment, and navigate the waters carefully.
This is readily expandable into other social problems. In many situations, the technical community may agree on the benefits of some change, and want to implement it in society. To their chagrin, non-technical people oppose the shift. The technical community would do well to pay attention to the lesson that metrication can teach.
The United States is the last industrialized nation to convert to the metric system. Many communities in the United States have already converted to the metric system or are making attempts to do so as quickly as possible. Examples of such groups include scientists, the military and the medical community. With the widespread use of computers it has become easy to quickly convert from one unit system to another using precise ratios established by scientific and governmental groups. The United States government has tried to support conversion, but has not been successful for a variety of reasons. There is a lack of popular support. Rather than advertising the benefits of an international standard and the advantages to the average person, only tables of conversions were provided with groups willing to help conversion when assistance was requested. A nation-wide conversion cannot occur without educating citizens and a strong government presence to oversee the process.
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