What was the primary motivation for most settlers in the western territories in the 1800s

The promise of free land.

Explanation:

Industrialization had not taken roots in the 1800s.

The main economic venture was farming which needed a land as a primary resource.

The discovery of new western territories led to caravans of settlers approaching to get the free land resource.

This makes the third option right.

the most famous of all the units fighting in cuba, the "rough riders" was the name given to the first u.s. volunteer cavalry under the leadership of theodore roosevelt. roosevelt resigned his position as assistant secretary of the navy in may 1898 to join the volunteer cavalry. the original plan for this unit called for filling it with men from the indian territory, new mexico, arizona, and oklahoma. however, once roosevelt joined the group, it quickly became the place for a mix of troops ranging from ivy league athletes to glee-club singers to texas rangers and indians.

the answer is definitley b!