Lake Washington is the second largest natural lake in the state of Washington. It is also perhaps one of the most famous case studies of lake eutrophication and subsequent recovery following the diversion of treated wastewater inputs in the 1960s. The lake has also been the subject of numerous sediment coring studies focused on the lake's response to eutrophication and contaminant inputs. Lake sediments provide a time-sequenced repository of information that integrates the changes in inputs from the water and airsheds that can be consulted at any time using a consistent set of methods. We collected and dated a core from Lake Washington in 2020 to evaluate long-term trends in carbon, nitrogen, phosphorus, algal pigments, algal toxins, metals, and polychlorinated biphenyls (PCBs). We present the coring study results within the context of the known history of significant human alteration of the lake beginning around 1860. Because there has been a long history of similar studies of Lake Washington sediments, we could compare our results to those reported in earlier studies. In general, the results were very similar across studies indicating the reproducibility and reliability of these methods for tracking water quality trends. Overall, this pilot study demonstrated the utility of collecting and analyzing a core using consistent methods. The result was a time series of relevant environmental variables spanning more than 150 years.