  We extend classical Maxwell field theory to a first quantized theory of the
photon by deriving a conserved Lorentz four-current whose zero component is a
positive definite number density. Fields are real and their positive (negative)
frequency parts are interpreted as absorption (emission) of a positive energy
photon. With invariant plane wave normalization, the photon position operator
is Hermitian with instantaneously localized eigenvectors that transform as
Lorentz four-vectors. Reality of the fields and wave function ensure causal
propagation and zero net absorption of energy in the absence of charged matter.
The photon probability amplitude is the real part of the projection of the
photon's state vector onto a basis of position eigenvectors and its square
implements the Born rule. Manifest covariance and consistency with quantum
field theory is maintained through use of the electromagnetic four-potential
and the Lorenz gauge.
