The first immigrant groups that made an impact on the culture and society of the western United States were called Pioneers.
The American pioneers emigrated from the settlements of the East coast to the settlements of the West Coast and colonized new areas.
The term refers especially to those who were going to populate any territory that had not previously been populated or cultivated by the descendants of European or American society, even though the territory may have been inhabited or used by indigenous peoples.
An important advance in the western settlement was the Homestead Act, which provided for formal legislation regulating the settlement process.