Site Regions and Site Districts of Ontario represent an early Ecological Land Classification (ELC) system originally developed by Angus Hills. This dataset was revised by the ELC Working Group in 2000 to better reflect new information and new technology. The Site Regions of Ontario was used for descriptive, planning, and resource management purposes. This upper level in its hierarchy was most useful for provincial and regional roll-ups of data and for strategic planning. Site Districts of Ontario is a more detailed lower (finer-scale) level of the hierarchy, and was more useful for detailed resource management prescriptions and other local and site planning applications. This layer is designed to be used as a spatial selection tool and as a background layer suitable for overlay and or intersection with numerous scales or current hydrologic data.