US customary system
In U.S. ,US customary system use for measurement.
The unit of length is foot ,yard,mile.
The unit of weight is pound.
US customary system is adopted by US from English unit system .In English unit system ,the unit of length if foot,the unit of mass is pound mass(lb),the unit of force is pound force(lbf).
we use the metric system (meter,liter) this is a lot easier to understand compared to the english system
Weights and Measures. ... This page explains the two most common systems of measurement: the metric system, used widely in Europe and most of the rest of the world, and the imperial or English system, now chiefly used in the USA.