<p>Urban development, industrialization, and vehicular emissions lead to the accumulation of heavy metals in urban soils. Background soils, those without direct pollution sources, reflect regional contaminant transport and industrial history. In soils, metals occur in distinct geochemical fractions that control their mobility and bioavailability. While metal speciation and bioavailability are well studied, cross-city variability in geochemical phase distributions is poorly understood. Pittsburgh (PGH) is a compelling case study for urban soil contamination given its legacy of steel production. New York City (NYC) and Los Angeles (LA), the only US cities with comparable datasets, provide a broader perspective on regional factors and metal distributions. Regional factors (local geology, soil properties, environmental conditions, and industrial history) shape metal enrichment and bioavailability. This study addresses this gap by evaluating total metal concentrations and geochemical phase distributions of Pb, Cd, Zn, Ni, and Mn in PGH, NYC, and LA. Sequential extractions of PGH soil samples were compared with similar analyses in NYC and LA, using the modified BCR method, to assess variations in metal partitioning across geochemical phases. We used the National Uranium Resource Evaluation (NURE) stream sediment dataset to assess regional Mn enrichment and geologic context. PGH exhibited higher Mn concentrations than NYC and LA. Industrial history contributes to Mn enrichment in PGH, but the patterns also suggest a possible role for vegetation in Mn retention and phase partitioning. In contrast, LA soils had the highest exchangeable metal fractions, suggesting greater metal bioavailability. Our findings highlight the complexity of urban soil metal contamination and the importance of considering both industrial legacies and environmental factors in determining metal bioavailability.</p>