In 1878 the [[United States]] signed the treaty called the ''Convention du Mètre.'' Since then, ''both'' the metric system and the [[United States customary units]] (miles, inches, pounds, etc.) have had legal status in the US. US Customary units are in fact defined by reference to metric units; that is, legally, an inch is ''defined'' to be exactly 25.4 millimeters. | In 1878 the [[United States]] signed the treaty called the ''Convention du Mètre.'' Since then, ''both'' the metric system and the [[United States customary units]] (miles, inches, pounds, etc.) have had legal status in the US. US Customary units are in fact defined by reference to metric units; that is, legally, an inch is ''defined'' to be exactly 25.4 millimeters. |