It is estimated by the transcriber Tom Blake, that holders of 200 or more slaves, constituting less than 1% of all U.S. slaveholders (fewer than 4,000 persons, one in 7,000 free persons, or 0.015% of the population) held an estimated 20–30% of all slaves (800,000 to 1,200,000 slaves). Nineteen holders of 500 or more slaves have been identified. The largest slaveholder was Joshua John Ward, of Georgetown, South Carolina, who in 1850 held 1,092 slaves, and whose heirs in 1860 held 1,130 or 1,131 slaveshe was dubbed "the king of the rice planters", and one of his plantations is now part of Brookgreen Gardens. The percentage of families that owned slaves in 1860 in various groupings of states was as follows: Historiography The historian Peter Kolchin, writing in 1993, noted that until the latter decades of the 20th century, historians of slavery had primarily concerned themselves with the culture, practices and economics of the slaveholders, not with the slaves. This was in part due to the circumstance that most slaveholders were literate and left behind written records, whereas slaves were largely illiterate and not in a position to leave written records. Scholars differed as to whether slavery should be considered a benign or a "harshly exploitive" institution. Much of the history written prior to the 1950s had a distinctive racist slant to it. By the 1970s and 1980s, historians were using archaeological records, black folklore and statistical data to develop a much more detailed and nuanced picture of slave life. Individuals were shown to have been resilient and somewhat autonomous in many of their activities, within the limits of their situation and despite its precariousness. Historians who wrote in this era include John Blassingame (Slave Community), Eugene Genovese (Roll, Jordan, Roll), Leslie Howard Owens (This Species of Property), and Herbert Gutman (The Black Family in Slavery and Freedom). See also Abolition of slavery timeline African American founding fathers of the United States American Descendants of Slavery (ADOS) American slave court cases The Bible and slavery Education during the slave period Fugitive slaves in the United States Historiography of slavery in the U.S. Human trafficking in the United States List of notable opponents of slavery Old Slave Mart, museum in Charleston, S.C. Origins of the American Civil War Reparations for slavery debate in the United States Reverse Underground Railroad Slave health on plantations in the United States Slave narrative Slavery among