This prolific US author promoted socialist views and anarchist causes as well as writing The Jungle.

The correct answer is Upton Sinclair.

This American author became a national name with his book "The Jungle." This fiction novel was based on the real working experiences of individuals within the meat packing industry during the early 20th century. The disgusting habits/practices of this industry and the terrible working conditions described gained national attention, eventually leading to president Teddy Roosevelt passing the Meat Inspection Act of 1907.