There are two Mahantango Creeks; one on either side of the Susquehanna River. That means one as as the border between Juniata and Snyder Counties, one in upper Dauphin County. The Alfred Buffington's book SONGS ALONG THE MAHANTANGO refers to the creek on the eastern side. On the east it's pronounced "Mah-kah-TANG-oh" and, on the westernr side, "Mah-hah-TANG-oh" as far as I have heard. Please consider that an informal survey. Bill Snyder (no, I'm not related to the Snyders of Snyder County)