The primary objective of USA’s seminal Clean Water Act “is to restore and maintain the chemical, physical and biological integrity of the Nation’s waters”. This poster highlights milestones in bioassessment progress and expansion since the Act was signed in 1972. At that time a few State agencies were using bioassessments in their water quality management programs. In 1973, aquatic biologists at the USEPA compiled and published methods for sample design, collection, processing, and analysis of fish, invertebrates, and algae. Throughout the 70’s and early 80’s, there were new insights for study design, sampling methods, improved taxonomic keys, and, with the help of fast, affordable computers, ecological data analysis and insights. However, the perceived, laborious processing of macroinvertebrate samples hindered the expansion of bioassessments to most States. This was remedied, in the late 80’s, with the development, training, and 1989 publication of U.S.EPA’s Rapid Bioassessment Protocols. Its emphasis on subsampling, (typically 100-300 specimens) reduced sorting and identification time by many fold, and, now, with the encouragement of agency managers, the spread of bioassessments took off, initially of wadeable stream macroinvertebrates. Concurrent to this bioassessment expansion, its relevance to the biological integrity objective of the Act became more apparent to researchers, practitioners, and managers. This, in turn, further expanded bioassessment research, field testing, surveillance and surveys from small streams to rivers, lakes, wetlands, and estuaries and to more use of fish and algae. Water quality management experienced further developments, including agency use of biocriteria to help regulate the restoration and maintenance of waters. Bioassessments are now allowing further refinement of environmental management through the development and expanding use of Biological Conditions Gradients. It appears the biology, along with hydrology and geomorphology, has come from step-child to the leading edge for management of aquatic systems.