This U.S. Geological Survey (USGS) Data Release contains locations and concentrations of metals in various size fractions in floodplain-core, streambed-sediment samples, and sediment deposited on the flood plain from the December 2015 flood and underlying soils collected from along the Middle Big River and tributaries in the Southeast Missouri Barite District from 2012 to 2015. All samples were analyzed either by inductively-coupled plasma-mass spectrometry (ICP-MS) or x-ray fluorescence (XRF). Concentrations of metals in quality-assurance samples are also presented to evaluate the effect of sample splitting and compare the U.S. Environmental Protection Agency (EPA) and USGS Missouri Water Science Center XRF units. Major and trace elements included in this data release include aluminum, antinomy, arsenic, barium, beryllium, bismuth, cadmium, calcium, cerium, cesium, chromium, cobalt, copper, gallium, indium, iron, lanthanum, lead, lithium, magnesium, manganese, molybdenum, nickel, niobium, phosphorus, potassium, rubidium, scandium, silver, sodium, strontium, sulfur, tellurium, thallium, thorium, tin, titanium, tungsten, uranium, vanadium, yttrium, and zinc. These data tables are provided as machine readable access to the tables in the following publication: Smith, D.C., and Schumacher, J.G., 2018, Distribution of mining-related trace elements in streambed and flood-plain sediment along the middle Big River and tributaries in the Southeast Missouri Barite District, 2012–15: U.S. Geological Survey Scientific Investigations Report 2018–5103, 89 p., https://doi.org/10.3133/sir20185103.