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.

the labor movement in the united states grew out of the need to protect the common interest of workers

for those in the industrial sector organized labor unions fought for better wages reasonable hours and safer working conditions

  in the 19th century trade unionism was mainly a movement of skilled workers.

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