Jefferson became the lead author of the United States Declaration of Independence. It was he who wrote some of the Declaration's best-known phrases, such as those saying that "all men are created equal" and have the right to "life, liberty and the pursuit of happiness."
The most important event of Jefferson's first term was the purchase of the Louisiana Territory in 1803. The purchase of this area, which until then belonged to France, made the United States twice as large. The president launched the Lewis and Clark Expedition to explore the new lands.
Jefferson was easily reelected in 1804, but his second term was not as successful as his first. A war between Britain and France has damaged US trade with Europe.
Well, it decreased the demand of Slave Labor.
Back then, the technology advancement , especially in agricultural sector, significantly increased the total production. This cause the demand of overall labor decreased. The northern US, who utilized more of this advancement more than their southern neighbor, manage to produce hundred times more output than the southern who still depended on their slave labor
So they (the slaves) were treated bad because they weren't considered human beings
