Read the statement from US Senator James Henry Hammond in 1858. "…No, you dare not to make war on cotton. No power on Earth dares to make war upon it. Cotton is king." What does this quote mean when talking about the growth of the plantation system and slavery?

The senator is talking about how the abolition of slavery will break the back of the cotton trade.

Explanation:

This statement is one of surety of the trade of cotton being lucrative enough for it to allow the overlooking of the race relations and the blatant systematic discrimination it brings upon the population.

The direct statement here is that Cotton is king and no moral stances can have a word against how powerful and how lucrative the trade is for the USA. The abolition of slavery can break the whole trade's profits and hence the senator is firmly on the side of the  industry.

the two colonies had the earliest laws mandating religious tolerance.