What was the least successful reform movement and why?
It could be argued that temperance, the movement to ban alcohol, was among the least successful American reform movements. The movement started in the U.S. in the early 1800s, part of the outgrowth of the Second Great Awakening, a religious movement that emphasized the importance of spirituality and the doing of good works.
The American Temperance Society was founded in 1826. The cause was largely championed by Protestant white women, who blamed alcohol for what they saw as men's neglect of their families. For example, the Woman's Christian Temperance Union (WCTU) was formed in 1873, led by Frances Willard and others. The temperance movement emphasized an evangelical form of Christianity and also had nativist, or anti-foreign, strains. For example, wine was a feature of religious ceremonies among Catholics and Jews, among other groups, so these groups were often anti-temperance.
Eventually, the 18th Amendment to the Constitution, ratified in 1919 and taking effect in 1920, outlawed the manufacture, sale, and transport of alcohol. However, during the period of Prohibition, the amendment largely resulted in the illegal manufacture of alcohol, the promotion of illegal activity surrounding the production of alcohol, and the loss of income for the federal government. Eventually, it was overturned by the 21st Amendment in 1933. After that time, the cause largely declined, though some religious groups in the U.S. still abstain from drinking alcohol.