Legacy sediments have been defined as sediments deposited throughout our stream and river valleys within the past two centuries. These sediments are found along streams that have a history of damming, particularly in the Piedmont province of Pennsylvania. We examined the macroinvertebrate community structure and functioning of the ecosystem via a leaf pack experiment in six, 2nd order streams in southern Lancaster County, Pennsylvania. Three of the streams are impacted by legacy sediments. Macroinvertebrates were collected using a Surber sampler and water quality and erosion rates were monitored at each stream. The impacted streams tended to have higher levels of phosphate, total suspended solids, and turbidity levels. We found that the legacy sediment impacted streams had a lower number of families compared to the control streams. MAIS scores were used to evaluate the streams; the control streams had two in the good category (16 & 13) and one stream in the upper fair range (12). The impacted streams all ranked in the middle of the fair category (8,9, & 10). The processing of organic matter appeared to be faster in the control stream then in the legacy sediment impacted streams. Those streams with significant water quality issues and erosion rates of legacy sediment appear to be compromised in both the macroinvertebrate community structure and subsequently the processing of organic material within the impacted study reaches.