I have bad news. Corporate personhood goes back much farther than Citizens United. We're talking the 1880s. Specifically, Santa Clara County v. Southern Pacific Railroad Company (1886)[1] which has been understood to affirm the protection of corporations under the Fourteenth Amendment[2].

The fourteenth amendment, as you recall, ends section 1 with "nor deny to any person within its jurisdiction the equal protection of the laws." Emphasis mine.

Two years later, in an opinion by Justice Stephen Johnson Field, in Pembina Consolidated Silver Mining Co. v. Pennsylvania (1888)[3] we find the definitive statement:

> The inhibition of the amendment that no state shall deprive any person within its jurisdiction of the equal protection of the laws was designed to prevent any person or class of persons from being singled out as a special subject for discriminating and hostile legislation. Under the designation of "person" there is no doubt that a private corporation is included.

While this doesn't necessarily means corporations have every legal protection natural persons do, the US has a long history of legal protection that corporations benefit from that we call personhood.

1. Santa Clara County v. Southern Pacific Railroad Company, 118 U.S. 394 (1886)

2. https://constitution.congress.gov/constitution/amendment-14/

3. Pembina Consolidated Silver Mining Co. v. Pennsylvania, 125 U.S. 181, 188-189 (1888)