What are Upton Sinclair and Lincoln Steffens known for doing

Upton Sinclair is famous for writing the book The Jungle, which exploits the horrible conditions of immigrants in industrialized cities during the early 1900's.

Lincoln Steffens is famous for being a muckracker, meaning he wrote for newspapers during the Progressive Era. Steffens also worked with Ida Tarbell, in revealing corruption (for example, Boss Tweed's crimes).