The Manifest Destiny which stated that the U.S. had a God-given right to all of the land in North America
I believe that immigrants migrated to the United States because of the abundance of resources and work opportunities. Many also fled from wars and sought safety for their families and themselves. Difficulties that immigrants from the 19th century faced ,and still face now, was the idea of Racism and also how society saw them. Many also had trouble finding places to live or people to communicate with. Many formed small groups and communities to stay together with the people of their own race and culture for safety.
Most single issued parties have been short lived.
