Early cotton farming in the United States is synonymous with the history of slavery in the United States. By the late 1920s around two-thirds of all African-American tenants and almost three-fourths of the croppers worked on cotton farms, and two in three black women from black landowning families were involved in cotton farming. Cotton farming was one of the major areas of racial tension in its history, where many whites expressed concerns about the mass employment of blacks in the industry and the dramatic growth of black landowners. Southern black cotton farmers faced discrimination from the north in particular, and strikes often broke out by black cotton farmers. Although the industry was badly affected by falling prices and pests in the early 1920s, the main reason is undoubtedly the mechanization of agriculture in explaining why many blacks moved to northern American cities in the 1940s and 1950s during the "Great Migration" as mechanization of agriculture was introduced, leaving many unemployed.[6] The Hopson Planting Company produced the first crop of cotton to be entirely planted, harvested and baled by machinery in 1944.[6]