"<span>Voters of a state or territory will vote on the slave issue, and it will be included in their state constitution" would be the best option, since popular sovereignty means that the people choose directly on certain issues--in this case slavery. </span>
Mexicans began to search for gold in Texas.
When young people migrate from a rural area which probably already is suffering from a low birthrate, this effectively eventually can create a "lack of life" in a certain place where after a decade or a few decades, a certain rural area can actually die out due to not enough young people being there anymore.