Peak-flow frequency analysis is crucial in various water-resources management applications, including floodplain management and critical structure design. Federal guidelines for conducting peak-flow frequency analyses, provided in Bulletin 17C, assume that the statistical properties of the hydrologic processes driving variability in peak flows do not change over time and so the frequency distribution of annual peak flows is stationary. Better understanding of long-term climatic persistence and further consideration of potential climate and land-use changes have caused the assumption of stationarity to be reexamined. This data release contains input and results of a study investigating hydroclimatic trends in peak streamflow in the Central United States, including nine states (Illinois, Iowa, Michigan, Minnesota, Missouri, Montana, North Dakota, South Dakota, and Wisconsin). Peak flow records from unregulated USGS streamgages were used to evaluate changes over 30-, 50-, 75-, and 100-year trend periods, all ending in water year 2020. Climate data used as input (Input.zip) includes RDS files (station*_meanDF.rds, where * is the streamgage station number) for each basin for each state containing basin-averaged climate data sourced from Wiezcorek and others (2022). Output of the climate analysis (Output.zip) is split by trend period (folders 30, 50, 75, and 100) and state (XX.zip, where XX is the two-letter state postal abbreviation). Each trend period and state pairing contains two Comma Separated Value (CSV) files. "ZZ_XX_results_US.csv" (ZZ is the trend period: 30, 50, 75, or 100) contains the statistical results of the climate analysis and “trend_pvals.csv” contains the p-values associated with the trends analyses from that statistical analysis. "climateTrends.html" describes the statistical methods applied. "TrendsFor*.html" files contain figures of the statistical results for each streamgage in a trend period.