The Mann Act, previously called the White-Slave Traffic Act of 1910, is a United States federal law, passed June 25, 1910 (ch. 395, ; codified as amended at ). It is named after Congressman James Robert Mann of Illinois.

In its original form, the act made it a felony to engage in interstate or foreign commerce transport of "any woman or girl for the purpose of prostitution or debauchery, or for any other immoral purpose". Its primary stated intent was to address prostitution, immorality, and human trafficking, particularly where trafficking was for the purposes of prostitution. It was one of several acts of protective legislation aimed at moral reform during the Progressive Era. In practice, its ambiguous language about "immorality" resulted in it being used to criminalize even consensual sexual behavior between adults. It was amended by Congress in 1978 and again in 1986 to limit its application to transport for the purpose of prostitution or other illegal sexual acts.

Background and motivation In the 19th century, many cities in the United States had designated legally protected areas of prostitution. Increased urbanization, as well as greater numbers of young women entering the workforce, led to greater flexibility in courtship without supervision. In this changing social sphere in the mid-1800s, concern over "white slavery" began. This term referred to women kidnapped for the purposes of prostitution and derives from Charles Sumner's 1847 description of the Barbary slave trade.

Numerous communities appointed vice commissions to investigate the extent of local prostitution, whether prostitutes participated in it willingly or were forced into it, and the degree to which it was organized by any cartel-type organizations. The second significant action at the local level was to close the brothels and the red-light districts. From 1910 to 1913, city after city changed previously tolerant approaches and forced the closing of their brothels. Opposition to openly practiced prostitution had been growing steadily throughout the last decades of the 19th century. The federal government's response was the Mann Act. The purpose of the act was to make it a crime to "transport or cause to be transported, or aid to assist in obtaining transportation for" or to "persuade, induce, entice, or coerce" a woman to travel. Many of the changes that occurred after 1900 were a result of tensions between social ideals and practical realities. Family form and functions changed in response to a complex set of circumstances that were the effects of economic class and ethnicity.

Rescuing sex trafficked young women Suffrage activists, especially Harriet Burton Laidlaw and Rose Livingston, took up the concerns. They worked in New York City's Chinatown and in other cities to rescue young white and Chinese girls from forced prostitution, and helped pass the Mann Act to make interstate sex trafficking a federal crime. Other groups, such as the Woman's Christian Temperance Union and Hull House, focused on children of prostitutes and poverty in community life while trying to pass protective legislation. The American Purity Alliance also supported the Mann Act.Bell, pp. 44–45.

Conspiracy narrative According to historian Mark Thomas Connelly, "a group of books and pamphlets appeared announcing a startling claim: a pervasive and depraved conspiracy was at large in the land, brutally trapping and seducing American girls into lives of enforced prostitution, or 'white slavery'. These white-slave tracts began to circulate around 1909.". Such narratives often misleadingly portrayed innocent girls "victimized by a huge, secret and powerful conspiracy controlled by foreigners" as they were drugged or imprisoned and forced into prostitution.

This excerpt from The War on the White Slave Trade was written by the United States District Attorney in Chicago:

While prostitution was widespread, studies by local vice commissions at the time indicate that it was "overwhelmingly locally organized without any large business structure, and willingly engaged in by the prostitutes."

Some contemporaries did question the idea of abduction and foreign control of prostitution through cartels. For example, noted radical and feminist Emma Goldman observed, "Whether our reformers admit it or not, the economic and social inferiority of woman is responsible for prostitution."

Legal application Although the law was created to stop forced sexual slavery of women, the most common initial use of the Mann Act was to prosecute men for having sex with underage girls. The phrase "immoral purpose" in the statute allowed a broad application of the law following its affirmation in

In addition to its stated purpose of preventing human trafficking, the law was used to prosecute unlawful premarital, extramarital, and interracial relationships. The penalties would be applied to men whether or not the woman involved consented, and if she had consented, the woman could be considered an accessory to the offense. Some attribute enactment of the law to the case of world-champion heavyweight boxer Jack Johnson. Johnson was known to be intimate with white women, some of whom he met at the fighting venue after his fights. In 1912, he was prosecuted, and later convicted, for "transporting women across state lines for immoral purposes" as a result of his relationship with a white prostitute named Belle Schreiber; the month prior to the prosecution, Johnson had been charged with violating the Mann Act due to traveling with his white girlfriend, Lucille Cameron, who refused to cooperate with the prosecution and whom he married soon thereafter.

The 1948 prosecution of Frank LaSalle for abducting Florence Sally Horner is believed to have been an inspiration for Vladimir Nabokov in writing his novel Lolita. Humbert Humbert, the narrator, at one point explicitly refers to LaSalle.

The Mann Act has also been used by the U.S. federal government to prosecute polygamists such as Mormon fundamentalists. Bigamy is illegal in the U.S. and all states have antipolygamy laws. Colorado City, Arizona; Hildale, Utah; Bountiful, British Columbia, northern Mexico are historic locations of several Mormon sects that practiced polygamy, although The Church of Jesus Christ of Latter-day Saints has expressly forbidden polygamy since the start of the 20th century. Sect leaders and individuals have been charged under the Mann Act when "wives" are transported across the Utah–Arizona state line or the U.S.–Canadian and U.S.–Mexican borders.

Notable prosecutions under the Mann Act