The Missouri Compromise—also referred to as the Compromise of 1820—was an agreement between the pro- and anti-slavery factions regulating slavery in the western territories. It prohibited slavery in new states north of the border of the Arkansas territory, excluding Missouri.
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In my opinion, JP Morgan treated his workers Terribly! he caused so many falling wages and he was careless about the health and safety of the workforces of his companies.
The British were the Western Imperialists you're looking for.