In what year was the Supreme Law of the Land in the US written?

The "Supreme Law of the Land" is the US Constitution.

Delegates to the Constitutional Convention in Philadelphia began writing the US Constitution in May 1787 and created the completed version on September 17, 1787. The Constitution was adopted by the delegates that day, was ratified by the states on June 21, 1788, and became effective March 4, 1789.