Upton Beall Sinclair Jr. (September 20, 1878 – November 25, 1968) was an American writer, muckraker, political activist and the 1934 Democratic Party nominee for governor of California who wrote nearly 100 books and other works in several genres. Sinclair's work was well known and popular in the first half of the 20th century, and he won the Pulitzer Prize for Fiction in 1943.