1866
positive
Metric System Legalized in the United States
Congress passed legislation making metric units legal for use in commerce across the country.
US Metric History Timeline
The United States has a long, uneven relationship with SI. These moments show how policy momentum advanced and stalled.
1875
positive
US Signs the Metre Convention
The United States joined the international treaty coordinating standards for measurement worldwide.
1975
positive
Metric Conversion Act
President Gerald Ford signed a law encouraging voluntary metric conversion and establishing national coordination.
1982
negative
US Metric Board Disbanded
The board tasked with metric transition support was dissolved, slowing momentum for standardization.
1999
negative
Mars Climate Orbiter Loss
A metric-imperial mismatch between teams contributed to the spacecraft's destruction during orbital insertion.
2023 - Present
neutral
Renewed Public Advocacy
Educators, engineers, and policy advocates are pushing for practical metric-first adoption in schools and industry.