Why did many americans believe it was important to expand u. s territory

To increase population.

Explanation:

During the time between 1803 & 1840 the Louisiana Purchase had taken place, it had doubled the size of the country which increased the population of the area. Therefore they had decided to expand even more over time for more population, it also is now referred to be called Manifest Destiny

abolish

do away with

unanimous

in complete agreement

secede

separate; break free

inauguration

starting a new position with a formal ceremony.

cooperationist

people who wanted the north to cooperate with the south

surrender

to give up

volunteer

perform a service for free

draft

involuntary service in military

retreat

withdraw; move away from enemy

advisor

expert who gives advice

explanation: