WASHINGTON — This is not your economy. It's not even your parents' economy. To a surprising degree, this is your great-grandparents' economy. Quietly, while attention has focused on the technology, finance and service sectors, businesses that stood astride 19th century industrial America but then collapsed have been resurrected to meet the needs of a feverishly industrializing world. In the process, much of what Americans think they know about their economy is being upended. Steel makers, railroads, mining concerns and agriculture, long considered part of a fading past, suddenly have bright futures. And segments of the economy long lauded as the...