The forced, coerced, and voluntary labor systems of the Spanish and early US–Mexico borderlands were as diverse as the territories where they predominated, and they evolved substantially over the course of three centuries. Spanish borderlands refers to an immense region that encompassed New Spain’s northern “interior provinces.” They were mostly inhabited and controlled by Indigenous peoples. In the 19th century, these provinces would become the modern border states and territories of California, Nevada, Arizona, New Mexico, Utah, Colorado, and Texas to the north; and Baja California, Sonora, Chihuahua, Coahuila, Nuevo León, and Tamaulipas to the south. Thousands of Indigenous, Black, mulatto, and mestizo people worked in coerced and unfree labor systems that ranged from outright slavery to encomienda, repartimiento, and debt peonage. New labor forms emerged with expanding global trade, economic reform, and industrialization in Europe and the United States. Compensated labor coexisted alongside forced labor in the colonial period, until it came to rival and, in some cases, replace involuntary labor by the early 19th century. Yet debt peonage and chattel slavery grew in importance during the same period. Workers themselves struggled to maintain autonomy and resisted through means that ranged from flight, malingering, and migration to outright rebellion.