We see a lot of social media messages about Puerto Rico’s status. Many call for statehood for Puerto Rico, some argue against it, and a few demand independence. But Leslie Bailey recently left a comment that is unique in bringing up a difference between Puerto Rico and the rest of the United States. “If Puerto Rico becomes a state,” Leslie said, “it will pressure the rest of the US to switch to the metric system.”

Leslie doesn’t say whether this would be a good thing or a bad thing. But it is a difference.

No metric system?

Currently, the U.S., Liberia, and Myanmar are the only nations that do not use the metric system. The standard U.S. system is the English system, or the Imperial system, as it used to be called. The U.S. generally measures distance in inches, yards, and miles; measures weight in pounds and ounces; and measures temperatures with the Fahrenheit scale.

The rest of the world uses the base 10 centimeters, meters, and kilometers, measures weights in grams, and uses the Celsius scale for temperature.

Puerto Rico does a little of both.

The history of the metric system in the United States

Thomas Jefferson asked French scientists for information about their new measurement system in the 1700s. The U.S. officially adopted the metric system in 1866, with the passage of the Metric Act of 1866. And in 1875, with the signing of the Treaty of the Meter. Also in 1975, under the Metric Conversion Act. And in 1988 with the Omnibus Trade and Competitiveness Act of 1988 which declared the metric system “the preferred system of weights and measures for United States trade and commerce.”

So the metric system is definitely the official measurement system for the United States, even though the imperial system (also now called the customary system) is the one people actually use most of the time.

But not in Puerto Rico, where distances along roads are measured in kilometers and speed is measured in miles per hour. Gas is sold in liters, while milk is sold in gallons.

Law 145 established in 1979 that both English and metric systems were legal in Puerto Rico. When this law was passed, Puerto Rico was facing complications because the gas pumps on the Island couldn’t handle gas price of $1.00 or more. Instead of requiring all gas stations to buy new pumps which could show three-digit prices, the legislature declared that gas would be sold by the half-gallon, showing the price for half gallons. They would then transition to sales of gasoline by the liter, which at that point was still under $1.00.

This was not a long-term solution to the problem of gas pumps, but it started Puerto Rico on the path of converting to the metric system.

The same plan was proposed in that same year in the rest of the United States. A spokesman for Shell Oil spoke up against the idea because it would be confusing. “All we know for sure,” he said, “is we can’t have two systems.”

Puerto Rico was willing to accept two systems.

Would statehood affect this?

You can hear claims that Puerto Rico clung to measuring distances in kilometers because some roads were marked before the U.S. arrived in Puerto Rico. Spain adopted the metric system in 1849. Did Puerto Rico quickly adopt the use of kilometers in the 49 years between Spain’s adoption of the metric system and its loss of Puerto Rico as a colony? Without also taking up centimeters and meters?

Is Puerto Rico simply more flexible?

Whatever reason you see for the use of both systems in Puerto Rico, statehood would not require a change. Congress has the power under the U.S. constitution to “fix the standard of weights and measures,” but has never forbidden the use of the old imperial system. Therefore, both the imperial and metric systems are legal for use in the United States.

Along with which language people should speak, this is a decision that rests with the states.

Would other states look at a new state of Puerto Rico, admire the KG signs, and finally make the switch? It will be interesting to see.




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