Urbanization is associated with novel habitats, pathogens, and a general decline in species and genetic diversity. Most studies on the genetic diversity of urban species focus on neutral loci like microsatellites that may not reflect diversity in fitness-related traits. In this study, we will determine the role of urbanization on the major histocompatibility complex (MHC class I) in House Finches, Haemorhous mexicanus. We have collected blood samples from at least 30 House Finches in each urban, suburban, and rural area in and around Fresno, California, and Phoenix, Arizona. Firstly, we hypothesize that rural House Finches will vary in genetic diversity at MHC compared to their suburban and urban conspecifics because of putative anthropogenic barriers to gene flow. We have PCR-amplified the polymorphic peptide binding region of MHC class I and will sequence them on the Illumina MiSeq platform. We will discuss the number of MHC alleles, and the number of private alleles, and estimate indices of sequence polymorphisms between the three population units. In addition, we will discuss population divergence using Jost's D estimate and STRUCTURE. This study will ultimately shed light on the associations between urbanization and the evolution of an adaptive immune gene.