Roughly what line of longitude was the westernmost boundary of the united states in 1790?

As the western frontier of the United States in 1790 was located at the Mississippi River, the line of longitude that was the westernmost boundary of the nation was 93º W meridian.

The Mississippi River springs 450 feet above sea level in Lake Itasca in northern Minnesota. Mississippi flows into the Gulf of Mexico approximatly 160 km below New Orleans, Louisiana. The Mississippi River is the second longest river in the United States; the longest is the Missouri River, which flows into the Mississippi River. The total length of the two rivers is approx. 6,270 km, and together they form the largest river system in the United States.

it gave them more rights