<Li> Technological and industrial history </Li> <Tr> <Td> Contributions by ethnicity (show) <Ul> <Li> African - Americans </Li> <Li> Native Americans </Li> </Ul> <Ul> <Li> Puerto Ricans </Li> </Ul> </Td> </Tr> <Ul> <Li> African - Americans </Li> <Li> Native Americans </Li> </Ul> <Li> African - Americans </Li>

What three technological innovations led to the expansion of the us