In the case in which it was first called upon to interpret [the Equal Protection] clause, the [U.S. Supreme] Court doubted whether "any action of a State not directed by way of discrimination against the [N]egroes as a class, or on account of their race, will ever be held to come within the purview of this provision."91 Nonetheless, in deciding the Granger Cases shortly thereafter [in 1877], the Justices seemingly entertained no doubt that the railroad corporations were entitled to invoke the protection of the clause.92 Nine years later [in 1886], Chief Justice Waite announced from the bench that the Court would not hear argument on the question whether the equal protection clause applied to corporations. "We are all of the opinion that it does."93

From FindLaw.com. For more on the subject of corporate personhood, click here.