WCTU is the acronym for the Women's Christian Temperance Union. As their name suggests, this was a group of women whose goal was to promote temperance. Temperance, in this context, means not drinking alcohol. So this was a group of women who were trying to get people to drink less alcohol.
The WCTU was founded in 1874. At this time, reformers like those who started the WCTU felt that drinking was a major problem that ended up hurting women and children. They felt that men would take their wages and buy alcohol instead of providing for their families. They felt that men would come home drunk and abuse their wives and children. For these reasons, they believed that it was important to get people to drink less and to try to get the government to (if possible) ban liquor. This was the goal of the WCTU.