Martin Luther King, Jr. (Credit: AP/Bill Ingraham) Throughout American history, religion has played a significant role in promoting social reform. From the abolitionist movement of the early 19th century to the civil rights movement of the 20th century, religious leaders have championed progressive political causes. This legacy is evident today in the group called religious progressives, or the religious left. The social gospel movement of the late 19th and early 20th centuries, as I have explored in my research, has had a particularly significant impact on the development of the religious left. What is the social gospel movement and why does it matter today? What was the social gospel? The social gospel’s origins are often traced to the rise of late 19th-century urban industrialization, immediately following the Civil War.