West Branch Mahantango Creek starts in the Allen Gap on Shade Mountain in Bald Eagle State Forest.
After about 3 miles (4.8 km), the creek turns southward, following the county line, but no longer paralleling Pennsylvania Route 35.
[3] Mahantango Creek continues approximately two miles eastward before flowing into the Susquehanna River.
[5] Out of the impaired upper portion of the West Branch Mahantango Creek watershed, 66% of the land is forest, 28% is devoted to agriculture, and 6% has other uses.
[5] A total of 8,747 pounds (3,968 kg) of sediment flow through West Branch Mahantango Creek every day.
[5] The average annual rainfall in the West Branch Mahantango Creek watershed between 1992 and 2011 was 39.30 inches (99.8 cm).
[5] Snyder County considers it possible that small amounts of flooding can cause damage to structures located along the creek.
[6] West Branch Mahantango Creek is located at an elevation of 390 feet (120 m) above sea level.
[8] The 69-foot (21-meter) long Oriental Bridge was built over West Branch Mahantango Creek in 1908 and was renovated in 1987.