Muckrakers were a group of reform-minded journalists, writers, and photographers in the United States during the Progressive Era (1890s-1920s) who sought to expose corruption and wrongdoing in established institutions, often through sensationalist publications. They provided detailed, accurate journalistic accounts of the political and economic corruption and social hardships caused by the power of big business in a rapidly industrializing United States. The term "muckraker" was initially pejorative when used by U.S. President Theodore Roosevelt in his speech of April 14, 1906, but it later took on favorable connotations of social concern and courageous exposition. Some of the key documents that came to define the work of the muckrakers were The Jungle, a book by Upton Sinclair that detailed the horrible effects of capitalism on workers in the Chicago meatpacking industry, and articles by Ida Tarbell that depicted Standard Oil tycoon John D. Rockefeller as a greedy, miserly monopolist. The work of muckrakers influenced the passage of key legislation that strengthened protections for workers and consumers. Some of the most famous muckrakers were women, including Ida Tarbell and Ida B. Wells.