The Mann Act, which made transporting women between states for "immoral purposes" a crime punishable by up to five years in jail and $5,000, on January 26, 1910, passed the US House en route to becoming law.
Sponsored by Congressman James Mann of Illinois, the White Slavery Act, as it was also known, came in response to lurid and sensational media accounts of an alleged international trade in women associated with America's large immigrant populations. The US attorney for Chicago had earlier in the year made headlines by claiming, without evidence, that an international criminal syndicate was kidnapping women in Europe and selling them to Chicago brothels.
The reactionary law was presented as an instance of progressive reform. Rep. Mann, a Republican, had earlier introduced the legislation that was to become the Pure Food and Drug Act and was supportive of women's suffrage.
Among those to be prosecuted under the Mann Act were heavyweight boxing champion Jack Johnson, actor Charlie Chaplin, music legend Chuck Berry, architect Frank Lloyd Wright, left-wing sociologist William I. Thomas, Canadian writer Elizabeth Smart and her lover, British poet George Parker.
http://www.wsws.org/articles/2010/jan2010/twih-j25.shtml#50