  The ESSENCE survey discovered 213 Type Ia supernovae at redshifts 0.1 < z <
0.81 between 2002 and 2008. We present their R and I-band photometry, measured
from images obtained using the MOSAIC II camera at the CTIO 4 m Blanco
telescope, along with rapid-response spectroscopy for each object. We use our
spectroscopic follow-up observations to determine an accurate, quantitative
classification and a precise redshift. Through an extensive calibration program
we have improved the precision of the CTIO Blanco natural photometric system.
We use several empirical metrics to measure our internal photometric
consistency and our absolute calibration of the survey. We assess the effect of
various potential sources of systematic bias on our measured fluxes, and we
estimate that the dominant term in the systematic error budget from the
photometric calibration on our absolute fluxes is ~1%.
