Answer:
Antislavery
Step-by-step explanation:
The northern states were mostly anti-slavery, and banned not only the selling and buying, but also the ownership of slavery.
On the other hand, the southern states were mostly pro-slavery, and allowed for the ownership of slaves, though the buying of foreign slaves were not allowed after certain time periods.
With this, it should mean that northern states (who is anti-slavery), would therefore send people that register with the anti-slavery movement mindset to Kansas in hopes of making it a free state.
~