The data presented includes chloride concentration and specific conductance in surface water collected from 33 wetlands in the Williston Basin of Montana and North Dakota, 2015-2017 as well as count data for three species of amphibians captured at each wetland. Data also includes concentrations of metals in bed sediment and larval amphibians collected from 32 and 12 wetlands, respectively in 2015-2016. Abundance of barred tiger salamanders (Ambystoma mavortium), boreal chorus frogs (Pseudacris maculata), northern leopard frogs (Lithobates pipiens) was estimated at 33 wetlands from 2015-2017. Surface water was collected in the summer from each wetland in 2015-2017 at the same time as the amphibian surveys and analyzed for chloride. Wetland area, wetland depth and estimate of the percent shallows was also collected as habitat covariates. Specific conductance data were collected at all wetlands in order to determine the locally derived Contamination Index (chloride concentration/specific conductance). Bed sediment was collected from several locations in 32 wetlands (3 in 2015 and 30 in 2016), homogenized and analyzed for a suite of 28 metals in 2015 and 2016. Larval amphibian tissues from the three species were also analyzed for the same suite of 28 metals in 2015 and 2016. Larval barred tiger salamanders, boreal chorus frogs and northern leopard frogs were collected in 12 wetlands (2 in 2015 and 10 in 2016) and analyzed for a suite of 26 metals. Northern leopard frogs and tiger salamander larvae were analyzed as individuals while boreal chorus frogs were composited due to their small size.