How did late nineteenth-century imperialism differ from earlier forms of european and american colonialism?

19th century imperialism was unique to earlier forms of imperialism because it was driven by political rather than economic agenda. The earlier forms of imperialism was driven by the desire to acquire land and push native Americans while 19th century imperialism was driven by desire to rule and conquer and was seen as a  source of prestige more than for source of economic opportunities. It explains why European imperialists were willing on to hold to some territories that had no resources.