What is one reason for the spread of slavery in the Southern colonies?

Slavery was popular in the Southern states because of the massive farming boom that happened because of an increase in certain crops: tobacco, sugar, and cotton being main ones.

Explanation:

Slaves provided cheap to completely free labor for plantations where the main purpose was to push massive amounts of crops for massive profit.

Sorry if this isn't what you meant, but I hope that this helps in some way.

the correct answer is "pioneers carried all of their possessions on long and dangerous trails".

the first wave of pioneers travelled in 1842. they were merely 100 people. the next year that sum climbed to 1000 men, women, and children. these people travelled around 2,000 miles to oregon in the hopes of a better life. although the first part of the trip didn't present many obstacles, as time and miles went by they learnt that threat came from simple things, like becoming ill due to unclean water or bad food.

the weather didn't much, as wagons couldn't protect them from storms. as they travelled through the desert, the intense heat caused wood to shrink. their own lips abscessed and split because of the dry air. the only cure for this was to rub axle grease on their lips.

even crossing rivers was dangerous. sometimes wheels were damaged by unseen rocks on shallow water. mud didn't much either. pioneers were afraid of indian attacks, but there aren't many records of fights between pioneers and native americans. accidents happened because of negligence, exhaustion, guns, and bad weather.

history says that 1 of 10 pioneers who travelled to oregon didn't survive the journey. diseases spread fastly because they didn't have doctors and medical care was ofently improvised. one of the most deadly diseases they came upon was cholera, which became a worldwide pandemia.