Eventually it makes a sharp turn southeast and leaves the county line.

It then turns northeast into Anthony Township, where it picks up the tributary McKee Run.

The stream then turns southeast and reaches its confluence with West Branch Chillisquaque Creek at the southern edge of Anthony Township.

[7] Much of the southern part of the watershed of County Line Branch lies over rock of the Onondaga and Old Port Formation.

The Chenango-Pope-Holly series is found in a small part of the lowest reaches of the watershed, near the stream's mouth.

The Hagerstown-Edom-Washington series is found in a much larger area in the southern part of the watershed.

[1] Agriculture and timbering are done in the upper reaches of the watershed of County Line Branch.

[8] A large number of native plants and animals live at the headwaters of County Line Branch.

Shrubs in this area include witch hazel, blackberry, spicebush, and mountain laurel.

There are also 23 herb species, including Christmas fern, Indian cucumber, veined skullcap, fleabane, wild sarsaparilla, and numerous others.

There are also ten species of birds at the stream's headwaters, including warblers, thrushes, woodpeckers, and others.