In this study, we investigate variation among steelhead in the Rogue River at presumed neutral genetic markers and markers from regions with known associations to ecologically-relevant traits (e.g. adult migration timing and residency vs. anadromy). We ask if late-summer adults are more genetically similar to early-summer or winter adults, and if half-pounders can be genetically classified as early- or late-migrating fish. Our study also adds to the growing body of research cataloguing the diversity of haplotypes associated with adult migration timing, and examines the extent to which individuals with intermediate migratory phenotypes can serve as a reservoir of early migration alleles. Finally, we discuss our results in context of work that proposes ecological and evolutionary explanations for the maintenance of the half-pounder life history.