This term is given to the part of the United States that was the center of most of the nation's economic activity until the 1970s and 1980s, when companies began relocating to warmer, more economically profitable parts of the country.

The area that was the center of economic activity was known as the economic hotbed.

Explanation:

Until the 1870s and 80s when the slowdown and the downturn of the booming American economy started, most of  the production and economic activity was based around the bustling states that were known as the hotbeds .

These hotbeds were states like California that had a warmer, more pleasant climate all around the year and were the most strategically important parts of the country for their economic activity as companies worked from there.

although the legal justifications for the trials and their procedural innovations were controversial at the time, the nuremberg trials are now regarded as a milestone toward the establishment of a permanent international court, and an important precedent for dealing with later instances of genocide and other crimes