Harford County is located along the upper western shore of the Chesapeake Bay, the largest estuary in Maryland. The Bay is approximately 200 miles long and varies from about 4 miles wide near Aberdeen to 35 miles wide near the Potomac River. While the average depth of the Bay is 21 feet, most of it is much shallower. In only a few areas of the Bay does the depth reach 100 feet.
The Chesapeake Bay Watershed encompasses six states: New York, Pennsylvania, Delaware, Maryland, West Virginia and Virginia, and the District of Columbia (Washington, D.C.) and covers 64,000 square miles. There were 18.2 million people living in the Chesapeake Bay Watershed and this is expected to increase to 20 million by 2030 and 21.1 million by 2040.