The eastern boundary of Mt. Harmony Elementary begins at the Anne Arundel County line at the Route 4 and Route 260 interchange and moves southeast along Route 260 (not to include drives along Route 260) to the intersection of Route 260 and Route 2. From here, the line moves south along Route 2 (not to include drives along Route 2) to the intersection of Route 2 and Mt. Harmony Road.

The southern boundary of Mt. Harmony Elementary begins at the out-fall of Hall Creek at the Patuxent River and follows the stream bed to a point where Route 4 crosses the stream. From this point, the line follows Route 4 south (to include drives along Route 4) to the intersection of Route 4 and Fowler Road. The line then moves in a northeasterly direction along Fowler Road, above Arbor Greene in a northeasterly direction to the intersection of West Mt. Harmony Road and Route 2.

Included in this school district are homes in Lyons Creek Overlook, Cedarwood, Apple Greene, Dunkirk Hall, Wards Meadows, Mac Donald Farms, Simpsons Farm, Owings Station, Calvert Estates, and Dunleigh.