America held promises of wealth and freedom for Europeans; in time, slavery became the key to the fulfillment of both. ‘Putting slavery into place’ describes the system of slavery initiated by European immigrants to the colonies. They chose to enslave only those who were different from them—Indians and Africans. When continued enslavement of Indians proved difficult or against colonists' self-interest, Africans and their descendants alone constituted the category of slave, and their ancestry and color came to be virtually synonymous with slave. In the mid-seventeenth century, colonists began formalizing slavery through legislation. By the 1700s black people were being held in lifelong, hereditary slavery, meaning that they and their descendants would be enslaved.