The evolutionary origins and adaptive significance of life-history variation among organisms have been long-standing questions since the inception of the field. We present data on the genomic underpinnings of life-history variation in populations of garter snakes characterized by two life-history ecotypes. The first, which inhabits mountain meadows of Lassen County, California exhibits a “slow-paced” life-history ecotype (M-slow) of slow growth, late maturation, small reproductive effort per bout, and long lifespan. The contrasting “fast-paced” life-history ecotype is found in lakeshore habitats (L-fast). Laboratory common garden and reciprocal transplant experiments have revealed both genetic and environment contributions to these ecotypes, which are further characterized by physiological differences in stress responses, differences in coloration, scale counts, and diet. Here we address the genomic underpinnings of this variation. We assessed both population structure and genomic variation between the two life-history ecotypes using whole-genome resequencing. Preliminary principal component analyses of >10 million SNPs in four populations representing both ecotypes (60 individuals) suggest that 14% of the variation in the genomic dataset is explained by differentiation among the ecotypes, and there is additional variation among populations consistent with isolation by distance. We aim to assess the genomic regions under selection that contribute to life-history variation, which will further our understanding of how complex traits such as lifespan can diverge rapidly and be maintained in systems with low levels of gene flow.