Larrys Creek is the only major watershed in Lycoming County entirely within the county. Measured directly, Lycoming County is about northwest of Philadelphia and east-northeast of Pittsburgh. It is from the mouth of Larrys Creek along the West Branch Susquehanna River to its confluence with the Susquehanna River at Northumberland, Pennsylvania. The source of Larrys Creek is in northern Lycoming County in Cogan House Township, just south of the hamlet of Steam Valley, at an elevation of It flows west-southwest through the village of Cogan House, and then under the Cogan House Covered Bridge.