The goal of Microbial Source Tracking (MST) is to identify sources of bacterial pollution in impaired waters. Forty six percent of the water bodies in Prince William County (PWC), Virginia, are classified as fecal impairments, an ideal situation for MST. This project utilized several MST techniques to identify sources of fecal pollution from seven locations on Cedar Run and Slate Run, seven locations on Neabsco Creek, two locations on Powell's Creek, and two locations from Quantico Creek. Samples were collected monthly for one year with two additional sets taken during storm events, one each during low flow and high flow conditions, totaling 216 samples with 24 isolates being analyzed per sample (5,184 total isolates). The samples were membrane filtered to obtain the enterococcal colonies used in Antibiotic Resistance Analysis (ARA) and Pulsed-Field Gel Electrophoresis (PFGE). Water samples were also analyzed for optical brighteners with a Turner 10-AU Fluorometer. Based on sample sites locations and apparent sources of contamination, two libraries, comprised of known source isolates from the PWC area, were used to analyze the ARA and PFGE patterns of the water sample isolates. The average rate of correct classification (ARCC) for the 1,250 isolate four-way split (human, domestic pets, wildlife, birds) urban ARA library was 95.8%. The ARCC for the 2,004 isolate four-way split (human, livestock, wildlife, birds) rural ARA library was 90.17%. The predominate sources found in the rural areas (Cedar and Slate Run, Quantico Creek) were livestock and wildlife and the sources found in the urban areas (Neabsco and Powell's Creek) were birds and wildlife. After the storm events, the livestock and wildlife signatures were slightly higher in the rural and urban areas, respectively. The results of this study provided city and county officials with information that will be used in the implementation of appropriate water improvement strategies.