The Stream Conditions of Chester County Biological Monitoring Network was established by the U.S. Geological Survey and the Chester County Water Resources Authority in 1969. Benthic-macroinvertebrate, habitat, and stream chemistry data were collected annually from 1998-2021 at 18 fixed location sites. Additionally, nine flexible location sites were selected and sampled annually from 1998-2021. Some of the flexible location sites were sampled more than once over the study period. All data were collected in the fall months (October-November) during baseflow conditions. The benthic-macroinvertebrate data collected was used to calculate six metrics and to establish an index of biotic integrity for each sample, while the habitat data was compiled to create a habitat score for each site and sample date. Three data files in .xlsx and .txt formats include: (1) the type and count of benthic macroinvertebrates in each sample, (2) the total number of organisms in the sample, the six calculated benthic-macroinvertebrate metrics, and the overall index of biotic integrity, and (3) the ten measured habitat characteristics and the overall habitat score for each site and date. The associated stream chemistry data collected for each site and date can be downloaded from the U.S. Geological Survey's National Water Information System.