The history of measurement science, or metrology, spans thousands of years. The bases for the English units of measurement have been defined and refined (and sworn at) over the past 6,000 years. Metric units are comparatively new, having been developed only over the past 240 years. These systems dominate modern measurement. This history will highlight the influences of practicality, philosophy, trade, agriculture, conquest, colonization, politics, and even adventure as the units have been defined and re-defined over centuries. It follows the development of technology from the most primitive to the most esoteric as the need for higher accuracy developed. The presentation will provide an abbreviated history of the English, or U.S. Customary, and the S.I metric systems. We will make a fast dash through the histories of the seven S.I. “base” units: length, mass, time, temperature, amount of substance, electrical current, and luminous intensity. We will then see how the base units are pulled together to define all the “derived” units. At the conclusion, we’ll take a look forward at where metrology is headed in the future. You’ve used measurement units all your life; now find out where they really came from and where they are going!