most african americans are the direct descendants of captives from west africa, who survived the slavery era within the boundaries of the present united states. as an adjective, the term is usually written "african-american". the first west africans were brought to jamestown, virginia in 1619. the english settlers treated these captives as indentured servants and released them after a number of years. this practice was gradually replaced by the system of race-based slavery used in the caribbean. all the american colonies had slavery, but it was usually the form of personal servants in the north (where 2% of the people were slaves), and field hands in plantations in the south (where 25% were slaves); by the beginning of the american revolutionary war 1/5th of the total population was enslaved. during the revolution, some would serve in the continental army or continental navy, while others would serve the british empire in lord dunmore's ethiopian regiment, and other units. by 1804, the northern states (north of the mason–dixon line) had abolished slavery. however, slavery would persist in the southern states until the end of the american civil war and the passage of the thirteenth amendment. following the end of the reconstruction era, which saw the first african american representation in congress, african americans became disenfranchised and subject to jim crow laws, legislation that would persist until the passage of the civil rights act of 1964 and voting rights act of 1965 due to the civil rights movement.