Based on the Preface, Introduction, and Chapters 1-4 of Ian Haney López's "Dog Whistle Politics: How Coded Racial Appeals Have Reinvented Racism and Wrecked the Middle Class," what is convict leasing?

In the book, convict leasing is described as the practice of leasing African-American prisoners as laborers for agricultural and industrial pursuits.
Since the thirteenth amendment made the exploitation of slave labor illegal, Southern whites turned to the practice of leasing African-American prisoners to fill their backlog of labor needs. Companies were all too willing to pay state convict systems to secure them workers. As a whole, millions of dollars filled the state coffers of Louisiana, Mississippi, South Carolina, North Carolina, Alabama, Georgia, Texas, and Florida during the turn of the century. In 1907, US Steel paid tens of thousands of dollars to more than 20 counties in Alabama for the privilege of securing a "steady supply of convict labor through at least 1912."
Healthy, "first-class" African-American prisoners were leased out at $18.50 a month, with the understanding that they would cut and load 4 tons of coal a day. The weakest laborers or "dead hands" were leased out at about $9 a month with the stipulation that they would produce a ton of coal a day. All laborers were lashed and tortured relentlessly by the guards in order to meet production goals. Many freed slaves were imprisoned under false pretenses so that the labor needs of companies could be filled. To save themselves from torture and certain death, many African-American families submitted to the practice of share-cropping in the hopes that powerful white landowners would protect them from the horrors of the convict system.
So, the convict leasing system essentially prolonged the practice of slavery in the South; as a practice, convict leasing did not end until the second world war.