The levee along the Mississippi, which is the largest man-mad structure in the world, was constructed with forced labor of various sorts, including convicts--The Parchman Farm, well known to blues lovers, was basically a forced labor camp--For first person accounts, see Alan Lomax's wonderful book, "The Land Where the Blues Began"--

The horrors of forced labor are an aspect of the racism in the South that were much discussed during the 60's and 60's Civil Rights movement, and, unfortunately, I guess the shock value has worn off, and stories like this don't get that much attention any more..thanks for letting us know about it, Toadfrog!!