The people who made the most money during the Gold Rush were "opportunistic" shopkeepers. Someone who is opportunistic is someone who is able to take advantage of any opportunity that presents itself. The word has a negative connotation, as it suggests that someone takes advantage of an opportnunity regardless of consequences or principles.
After being kidnapped from West Africa and enslaved in Boston, Phillis Wheatley became the first African American and one of the first women to publish a book of poetry in the colonies in 1773. Who Was Phillis Wheatley?