We report the total and differential cross sections for J/ψ photoproduction obtained using the
large acceptance GlueX spectrometer at the 12 GeV JLab accelerator over the full near-threshold
kinematic region. The GlueX experiment uses tagged linearly-polarized photon beam from
coherent Bremsstrahlung off a thin diamond. Charmonium photoproduction near threshold, under
certain assumptions including gluon exchange and factorization, can be used to study important
aspects of the gluon structure of the proton, such as the gluon GPD, the gravitational form factors,
the mass radius of the proton, and the anomalous contribution to the proton mass. In the measured
cross sections we find evidence for possible contributions beyond gluon exchange. The results
are compared to a wide range of theoretical predictions including GPD calculations and models
with open-charm intermediate states. Photoproduction near threshold of charmonium states with
opposite-to-photon parity offer another opportunity, complementary to the J/ψ, to understand the
reaction mechanism of the charmonium photoproduction. While we see some evidence for such
states, comprehensive studies of such higher-mass charmonia can be done only with the proposed
JLab energy upgrade. An electron beam energy of up to 22 GeV significantly increases the photon
flux and polarization in the corresponding threshold regions allowing for precise cross section and
polarization measurements there.