<Tr> <Th> Track gauge </Th> <Td> 1,435 mm (4 ft 8 ⁄ in) standard gauge </Td> </Tr> <Tr> <Td_colspan="2"> <Table> <Tr> <Th> Map of the line </Th> </Tr> <Tr> <Td> </Td> </Tr> </Table> </Td> </Tr> <Table> <Tr> <Th> Map of the line </Th> </Tr> <Tr> <Td> </Td> </Tr> </Table> <Tr> <Th> Map of the line </Th> </Tr>

Where did most of the workers who built the transcontinental railroad come from