Nowhere were the wartime effects greater than in Houston, which in 1940 was a city of 400,000 population dependent on shipping and oil. The war dramatically expanded the city's economic base, thanks to massive federal spending. Energetic entrepreneurs, most notably George Brown, James Elkins and James Abercrombie, landed hundreds of millions of dollars in federal wartime investment in technologically complex facilities. Houston oil companies moved from being refiners and became sophisticated producers of petrochemicals. Especially important were synthetic rubber and high octane fuel, which retained their importance after the war. The war moved the natural gas industry from a minor factor to a major energy source; Houston became a major hub when a local firm purchased the federally-financed Inch pipelines. Other major growth industries included steel, munitions, and shipbuilding.