Since its inception, the International Citrus Genome Consortium (ICGC) has pursued development of freely available genomics resources and tools for the benefit of the citrus research community; these efforts were conducted by citrus scientists in concert with researchers from some of the world's major genome sequencing centers and corporations. An early ICGC goal was to produce a full-length genome assembly. Two reference genome sequences were made publicly available in January 2011, from a 'Clemenules' clementine-derived haploid and diploid 'Ridge Pineapple' sweet orange, produced using Sanger and 454 sequencing technologies respectively. Subsequent work has proceeded to improve the assemblies and their annotation; a brief summary of their characteristics and status of the assemblies will be presented. As sequencing technology has evolved and costs have dramatically decreased, other citrus genomes have been sequenced (the diploid 'Clemenules', 'Ponkan', 'Willowleaf', 'W. Murcott' mandarins; 'Siamese Sweet' and 'Chandler' pummelo; and sour orange, among others). A comparative analysis of these genomes has made it possible to describe the genomic contributions from ancestral outbred populations to major cultivar types, and to propose likely underlying models. The results confirmed previous reports that clementine arose from a hybridization event between 'Willowleaf' mandarin and sweet orange. Further, introgressions of Citrus reticulata and Citrus maxima germplasm, long implicated in its ancestry, clearly defined the segmented mosaic genome of sweet orange, through the ancient admixture of these species. Finally, sour orange was found to be a direct hybrid of a pummelo and mandarin. Interestingly, although the two pummelos sequenced appear to have their derivations from a single wild species (C. maxima), the mandarins sequenced reveal ancestral admixture of C. maxima with C. reticulata. Implications and future directions for collaborative research will be discussed.