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Bromine and iodine species are precursors for forming disinfection byproducts in finished drinking waters. Our study incorporates spatial and temporal data to quantify concentrations of inorganic (bromide (Br − ), iodide (I − ), and iodate (IO 3 − )), organic, and total bromine (Br T ) and iodine (I T ) species from 286 drinking water sources and 7 wastewater effluents across the United States. Br − ranged from <5−7800 μg/L (median of 62 μg/L in surface water (SW) and 95 μg/L in groundwater (GW)). I − was detected in 41% of SW (1−72 μg/L, median = <1 μg/L) and 62% of GW (<1−250 μg/L, median = 3 μg/L) samples. The median Br − /I − ratio in SW and GW was 22 μg/μg and 16 μg/μg, respectively, in paired samples with detect Br − and I − . Br T existed primarily as Br − , while I T was present as I − , IO 3 − , and/or total organic iodine (TOI). Inorganic iodine species (I − and IO 3 − ) were predominant in GW samples, accounting for 60−100% of I T ; however, they contributed to only 20−50% of I T in SW samples. The unknown fraction of I T was attributed to TOI. In lakes, seasonal cycling of I-species was observed and was presumably due to algal productivity. Finally, Spearman Rank Correlation tests revealed a strong correlation between Br − and I T in SW (R Br − ,IT = 0.83) following the log 10 (Br − , μg/L) = 0.65 × log 10 (I T , μg/L) − 0.17 relationship. Br − and I − in treated wastewater effluents (median Br − = 234 μg/L, median I − = 5 μg/L) were higher than drinking water sources.