Final answer:
Nativists would most likely oppose immigration during the later half of the 1800s.
Step-by-step explanation:
The group of people who would most likely oppose immigration during the later half of the 1800s are Nativists. Nativists believed that anyone who was not born in the United States is 'undesirable' and that American culture is superior to all others.
Learn more about Opposition to immigration during the 1800s