  We present the catalog of 477 spectra from the Serendipitous Extragalactic
X-ray Source Identification (SEXSI) program, a survey designed to probe the
dominant contributors to the 2-10 keV cosmic X-ray background. Our survey
covers 1 deg^2 of sky to 2-10 keV fluxes of 10^-14 erg cm^-2 s^-1, and 2 deg^2
for fluxes of 3 x 10^-14 erg cm^-2 s^-1. Our spectra reach to R <24 and have
produced redshifts for 438 hard X-ray sources. The vast majority of the 2-10
keV-selected sample are AGN with redshifts between 0.1 and 3. We find that few
sources at z<1 have high X-ray luminosities, reflecting a dearth of high-mass,
high-accretion-rate sources at low redshift, a result consistent with other
recent wide-area surveys. Half of our sources show significant obscuration,
with N_H>10^22 cm^-2, independent of unobscured luminosity. We classify 168
sources as emission-line galaxies; all are X-ray luminous objects with optical
spectra lacking both high-ionization lines and evidence of a non-stellar
continuum. The redshift distribution of these emission-line galaxies peaks at a
significantly lower redshift than does that of the sources we spectroscopically
identify as AGN. We conclude that few of these sources can be powered by
starburst activity. Stacking spectra for a subset of these sources, we detect
[Ne V] emission, a clear signature of AGN activity, confirming that the
majority of these objects are Seyfert 2s in which the high-ionization lines are
diluted by stellar emission. We find 33 objects lacking broad lines in their
optical spectra which have quasar X-ray luminosities (Lx>10^44 erg s^-1), the
largest sample of such objects identified to date. In addition, we explore 17
AGN associated with galaxy clusters and find that the cluster-member AGN sample
has a lower fraction of broad-line AGN than does the background sample.
