The first enslaved Africans sent to the English colonies were classified as indentured servants, with legal standing similar to that of contract-based workers coming from Britain and Ireland. However, by the middle of the 17th century, slavery had hardened as a racial caste, with African slaves and their future offspring being legally the property of their owners, as children born to slave mothers were also slaves (partus sequitur ventrem). As property, the people were considered merchandise or units of labour, and were sold at markets with other goods and services