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There was not one specific date, Westward Expansion happened over a long period of time.
how did washington view on slavery evolved over time
They came over to californiia during the gold rush, along with the russians, japanese, etc.
Slavery goes back as far as History not only in West Africa but all over the world and it is still with us.
In the election of 1848, the Democrats chose a platform that remained silent on slavery. Nominee Lewis Cass was pro-slavery, so many anti-slavery Democrats walked out of the Baltimore convention to begin the Free Soil party.
It would help ease the debate over slavery.
The controversy over the new territories in westward expansionism primarily revolved around the issue of whether these territories would allow or ban slavery. This dispute heightened tensions between the North and the South as it directly impacted the balance of power in Congress and threatened the delicate compromise that had been established between free and slave states. The debates ultimately led to the Missouri Compromise, the Compromise of 1850, and other legislative agreements to manage the issue of slavery in the new territories.
Missouri Compromise
The main constitutional arguements during the debate over slavery were representation in Congress, importation of slaves, and the Bill of Rights.
Some possible results of the growing sectional debate over slavery include humanitarian results. For example, when people treat others fairly, all will be educated and respected and slavery will stop growing.
Abraham Lincoln and Stephen Douglas were the two participants in the great debate over slavery prior to the election of 1858.
Because of the debate over slavery
Republican
The admission of new states to the union and Dred Scott decision fueled the ongoing debate over slavery. (I got this off of ChaCha.com)
Stephen A. Douglas
to abolish it
Admitting California into the Union in 1850 gave raise over the debate over slavery. It was against Federal law of the confederacy to harbor slaves in free states.