The large expansion of slavery refers to the significant growth and entrenchment of the institution of slavery in the United States, particularly in the 19th century, as agricultural economies, especially in the South, relied heavily on enslaved labor for the cultivation of cash crops like cotton and tobacco. This expansion was fueled by increased demand for these crops, advancements in agricultural technology, and the territorial growth of the nation, which led to the spread of slaveholding practices into new regions.