Mahantango, sometimes spelled as Mohentango, was on both sides of the Susquehanna River. It was split by The river; the Eastern portion became Mahanoy Twp, Northumberland County, the Western portion became Perry County. Before 1772, the area was named Lancaster County. After 1772 it was in Northumberland County. Today the Western portion is in what is today's Snyder County. Snyder County was formed in 1855, from Union County and Union County was formed in 1813 from Northumberland County, which was formed in 1772 from parts of Lancaster, Berks, Bedford, Cumberland, and Northampton Counties.