<Li> 4, 5, and 6 WTC: 500,000 sq ft (50,000 m) each </Li> <Li> 7 WTC: 1,868,000 sq ft (170,000 m) </Li> <Tr> <Th> Lifts / elevators </Th> <Td> 1 and 2 WTC: 99 each </Td> </Tr> <Tr> <Th_colspan="2"> Design and construction </Th> </Tr>

When were the twin towers in new york built