Opponents of new slave states pointed to which 1787 measure that forbade slavery's extension into the northwest?

1. Northerners justifying opposition to new slave states cited the founders' own precedents. 2. They pointed to statements of Washington and Jefferson and to the Ordinance of 1787. 3. That ordinance forbade the extension of slavery into the northwest. 4. The Missouri Compromise came in 1820 and drew a different line, a generation later. _Source: "An Outline of American History" (USIA, 1990, public domain), Ch 5 "Sectional Conflict"_