Farmers who owned more than 20 slaves were called Planters.
America was clearly divided between North and South until the Civil War. The North had a more city feeling to it, with factories and active workers. The South was more dependent on agriculture and had a very high number of slaves who worked as cheap labor. Many of these slaves worked in cotton and generated large profits for their owners. During that era, less than a quarter of the population of the South owned slaves and among these owners, most (~88%) were farmers and owned less than 20 slaves. Only 12% of these owners were planters. It has been estimated that only 3000 planters owned more than 100 slaves and just 14 owned more than 1000 slaves.
As a side note, it is interesting to note that 8 US presidents owned slaves while they were president.