Berkshire first bought a stake in the country's largest railroad operator in 2007; in November it announced that it was acquiring the 77% it did not own for $26.3 billion in cash and stock. It was a classic Warren Buffett acquisition: unglamorous and steadily profitable. It also came with a CEO, Matthew K. Rose, who is young (he's 50) and capable enough to be seen as a candidate to run Berkshire's operations when Buffett no longer can. Most interestingly, it made clear that Berkshire Hathaway, which rose to prominence from the 1970s to the 1990s as an investment fund with a few businesses attached, had chiefly become a conglomerate making a big bet on the future of America's industrial economy.