Why must cartographers change the shapes of places on maps?

Because they cannot accurately project them and there is always distortion.

Explanation:

A feature such as the shape of a place cannot be accurately projected or represented on a map because of the problem of distortion and a cartographer has to decide what type of map he is making so he can make the details of the map as accurate as possible.

lincoln declared that slavery should not be allowed to spread into the new states, and of course this angered the south at the time.