Urbanization has the potential to alter the evolutionary trajectory of immune genes in wildlife, yet its impact on toll-like receptors (TLRs), which recognize conserved pathogenic molecules during an innate immune response, is unexplored. This study examines how habitat fragmentation and environmental pressures along an urban-rural gradient in the Fresno, California region affect TLR evolution in a resident bird, the house finch (Haemorhous mexicaus). We hypothesize that reduced gene flow in urban areas will lead to allelic differentiation and variation in molecular evolution at specific codons in four TLR genes: TLR2B, TLR3, TLR4, and TLR15. House finch DNA was collected across this gradient in 2024 and the TLRs are currently being characterized through Sanger sequencing. The results of these analyses will be discussed, providing insight into how urbanization influences immune gene diversity and molecular evolution. By demonstrating how urbanization shapes immune system evolution in a common songbird, this research holds potential implications for conservation strategies aimed at maintaining genetic diversity and resilience in urban wildlife populations.