  We present the first catalog of active galactic nuclei (AGN) detected by the
LAT, corresponding to 11 months of data collected in scientific operation mode.
The First LAT AGN Catalog (1LAC) includes 671 gamma-ray sources located at high
Galactic latitudes (|b| > 10 deg) that are detected with a test statistic (TS)
greater than 25 and associated statistically with AGNs. Some LAT sources are
associated with multiple AGNs, and consequently, the catalog includes 709 AGNs,
comprising 300 BL Lacertae objects (BL Lacs), 296 flat-spectrum radio quasars
(FSRQs), 41 AGNs of other types, and 72 AGNs of unknown type. We also classify
the blazars based on their spectral energy distributions (SEDs) as archival
radio, optical, and X-ray data permit. In addition to the format 1LAC sample,
we provide AGN associations for 51 low-latitude LAT sources and AGN
"affiliations" (unquantified counterpart candidates) for 104 high-latitude LAT
sources without AGN associations. The overlap of the 1LAC with existing
gamma-ray AGN catalogs (LBAS, EGRET, AGILE, Swift, INTEGRAL, TeVCat) is briefly
discussed. Various properties--such as gamma-ray fluxes and photon power law
spectral indices, redshifts, gamma-ray luminosities, variability, and archival
radio luminosities--and their correlations are presented and discussed for the
different blazar classes. We compare the 1LAC results with predictions
regarding the gamma-ray AGN populations, and we comment on the power of the
sample to address the question of the blazar sequence.
