A "Muckraker" refers to journalists and writers in the early 20th century who investigated and exposed corruption, social injustices, and abuses of power in politics and business. The term originated from Theodore Roosevelt, who used it to describe those who focused on the negative aspects of society, akin to a character in John Bunyan's "Pilgrim's Progress" who rakes up muck. Muckrakers played a crucial role in the Progressive Era by raising public awareness and prompting reforms. Notable muckrakers include Upton Sinclair, whose book "The Jungle" revealed unsanitary conditions in the meatpacking industry, and Ida B. Wells, who fought against lynching and racial injustice.