Question

The Missouri compromise of 1820 involved land gained from blank purchase

Answer 1

I think your answer would be The Lousiana Purchase.

This is how I got my answer: https://www.loc.gov/rr/program/bib/ourdocs/missouri.htm

"In an effort to preserve the balance of power in Congress between slave and free states, the Missouri Compromise was passed in 1820 admitting Missouri as a slave state and Maine as a free state. Furthermore, with the exception of Missouri, this law prohibited slavery in the Louisiana Territory north of the 36° 30´ latitude line. "(Missouri Compromise)

Work Cited:

"Primary Documents in American History.” Planning D-Day (April 2003) - Library of Congress Information Bulletin, Victor, www.loc.gov/rr/program/bib/ourdocs/missouri.html.

Answer 2

Louisiana Purchase. Thomas Jefferson purchased this from Napoleon.