<Tr> <Td> 29 </Td> <Td> </Td> <Td> CenterPoint Energy </Td> <Td> </Td> <Td> 279 </Td> </Tr> <Tr> <Td> 30 </Td> <Td> </Td> <Td> HollyFrontier </Td> <Td> </Td> <Td> 289 </Td> </Tr> <Tr> <Td> 31 </Td> <Td> </Td> <Td> Energy Future Holdings </Td> <Td> </Td> <Td> 292 </Td> </Tr> <Tr> <Td> 32 </Td> <Td> </Td> <Td> Kinder Morgan </Td> <Td> </Td> <Td> 294 </Td> </Tr>

The economy of the plains region of texas was historically dominated by