When did the United States first establish its measuring system, and who was responsible for picking the system?

Answer: The United States does not have an official "national measuring system" in the way that countries have officially adopted the International System of Units (SI). Historically, the US has used a combination of British imperial units and units that have evolved domestically. The use of these units was largely informal and varied from colony to colony before the establishment of the country.

After the Declaration of Independence in 1776 and the establishment of the United States, the Constitution, which was ratified in 1789, gave Congress the power "to coin Money, regulate the Value thereof, and of foreign Coin, and fix the Standard of Weights and Measures." However, it wasn't until 1828 that the US officially standardized its weights and measures based on the English system.

The decision to use these units wasn't made by a single individual but rather developed out of historical usage and was eventually legislated by the federal government. One key figure who had a significant impact on the discussion about measurement in the United States was Thomas Jefferson. He advocated for a decimal-based measurement system and even proposed a new system of measures that included elements of both the existing English units and a decimal-based system similar to what would later become the metric system. Despite this, the US continued to use traditional English units, and it wasn't until the late 19th century that the metric system was legally recognized, although not widely adopted.