Background: The international Dog10K project aims to sequence and analyze several thousand canine genomes. Incorporating 20x data from 1,987 individuals, including 1,611 dogs (321 breeds), 309 village dogs, 63 wolves and four coyotes, we identify genomic variation across the canid family, setting the stage for detailed studies of domestication, behavior, morphology, disease susceptibility and genome architecture and function. Results: We report the analysis of >48M single nucleotide, indel, and structural variants spanning the autosomes, X chromosome and mitochondria. We discover more than 75% of variation for 239 sampled breeds. Allele sharing analysis indicates that 94.9% of breeds form monophyletic clusters and 25 major clades. German Shepherd Dogs and related breeds show the highest allele sharing with independent breeds from multiple clades. On average, each breed dog differs from the UU_Cfam_GSD_1.0 reference at 26,960 deletions and 14,034 insertions greater than 50bp, with wolves having 14% more variants. Discovered variants include retrogene insertions from 926 parent genes. To aid functional prioritization, single nucleotide variants were annotated with SnpEff and Zoonomia phyloP constraint scores. Constrained positions were negatively correlated with allele frequency. Finally, the utility of the Dog10K data as an imputation reference panel is assessed, generating high confidence calls across varied genotyping platform densities including for breeds not included in the Dog10K collection. Conclusions: We have developed a dense dataset of 1,987 sequenced canids that reveals patterns of allele sharing, identifies likely functional variants, informs breed structure, and enables accurate imputation. Dog10K data are publicly available