James McWilliams writes today in the Freakonomics blog that advocates of grass-fed beef are mistaken in asserting that until very recently, all beef was grass-fed. He’s right, as far as he goes: Agriculture experts advocated raising beef cattle on corn as long ago as the early nineteenth century. As one commenter pointed out, advocacy and practice are not the same thing. But they’re not always that far apart, either, and so I think it’s worth thinking about why progressive nineteenth-century agriculturalists thought corn-fed was better.