  The Blanco Cosmology Survey is 4-band (griz) optical-imaging survey that
covers ~80 square degrees of the southern sky. The survey consists of two
fields roughly centered at (RA,DEC) = (23h,-55d) and (5h30m,-53d) with imaging
designed to reach depths sufficient for the detection of L* galaxies out to a
redshift of one. In this paper we describe the reduction of the survey data,
the creation of calibrated source catalogs and a new method for the separation
of stars and galaxies. We search these catalogs for galaxy clusters at z< 0.75
by identifying spatial over-densities of red-sequence galaxies. We report the
coordinates, redshift, and optical richness, Lambda, for 764 detected galaxy
clusters at z < 0.75. This sample, >85% of which are new discoveries, has a
median redshift of 0.52 and median richness Lambda(0.4L*) of 16.4. Accompanying
this paper we also release data products including the reduced images and
calibrated source catalogs. These products are available at
http://data.rcc.uchicago.edu/dataset/blanco-cosmology-survey .
