  We report on an XMM-Newton observation of the z=1.055 quasar and Giga-hertz
Peaked Spectrum (GPS) source 3C 287. Our 62.3 ksec observation provides an
exceptional X-ray view of a prominent member of this important subclass of
active galactic nuclei (AGN). The X-ray spectra of 3C 287 are consistent with a
simple absorbed power-law with a spectral index of Gamma = 1.72 +/- 0.02. Our
fits imply a bolometric luminosity of L = 5.8 +/- 0.2 E+45 erg/s over the
0.3-10.0 keV band; this gives a mass lower limit of M > 4.6 E+7 Msun, assuming
X-rays contribute 10% of the bolometric luminosity and radiation at the
Eddington limit. Iron emission lines are common in the X-ray spectra of many
AGN, but the observed spectra appear to rule out strong emission lines in 3C
287. The simple power-law spectrum and absence of strong emission lines may
support a picture where our line of sight intersects a relativistic jet.
Milliarcsecond radio imaging of 3C 287 appears to support this interpretation.
We discuss our results in the context of different AGN sub-classes and the
possibility that GPS sources harbor newly-formed black hole jets.
