Mendenhall Order

The Mendenhall Order marked a decision to change the fundamental standards of length and mass of the United States from the customary standards based on those of England to metric standards (Mendenhall 1922). It was issued on April 5, 1893, by Thomas Corwin Mendenhall, superintendent of the U.S. Coast and Geodetic Survey, with the approval of the United States Secretary of the Treasury, John Griffin Carlisle. The order was issued as the Survey's Bulletin No. 26 - Fundamental Standards of Length and Mass.

In October 1834, the United Kingdom Houses of Parliament were destroyed in a fire, and the British standards of length and mass were also destroyed. "When the new imperial standards to replace them were completed in 1855, two copies of the yard and one copy of the avoirdupois pound were presented to the United States" (Barbrow & Judson 1976, 9). These were superior to the yard then in use, so one of them was adopted as the United States national standard yard. These yards were taken to England and re-compared with the imperial yard in 1876 and 1888. The pound provided by the United Kingdom agreed with the United States mint pound, which remained the national standard according to Barbrow and Judson. Hockert (2015) claims the UK pound replaced the mint pound.

These were the fundamental standards for customary length and mass measurements in the United States, but the Office of Weights and Measures had other standards for metric measurements.

In 1866, the Congress passed a law which allowed, but did not require, the use of the metric system. Included in the law was a table of conversion factors between the traditional and metric units. The U.S. Coast and Geodetic Survey Office of Weights and Measures had on hand a number of metric standards, and selected the iron “Committee Meter” and the platinum “Arago Kilogram” to be the national standards for metric measurement; the standard yard and pound previously mentioned continued to be the standards for customary measurements. (Barbrow & Judson 1976, 10).

...
Wikipedia