What was the name given to journalists who focused on the poverty and corruption in the cities?
Journalists who focused on poverty and corruption were known as "muckrakers".
Today "muckrakers" would be termed "investigative reporters".
These journalists who worked primarily with the most popular magazines of the era focused their energies on the underlying causes of the problems of society.
While some journalists had always pointed out the flaws in society the trend of pointing fingers and attaching blame for the difficulties of society trended in the early 1900's in journals such as Collier's, McClures and The New work Evening Post.