Tioga County, NY
History
In 1791 Tioga County was founded by another division of territory from Montgomery County (also founded then were Herkimer and Otsego counties. Tioga County was at this time much larger than the present county, including present-day Broome and Chemung counties and parts of Chenango and Schuyler counties.Tioga County was reduced in size in 1798 by the splitting-off of Chemung County (which also included part of the present Schuyler County and by the combination of a portion with a portion of Herkimer County to create Chenango County. In 1806 it was further reduced by the splitting-off of Broome County.
Source: Wikipedia
Modern Day Adjacent Counties
Cortland County - northeastBroome County - east
Susquehanna County, Pennsylvania - southeast
Bradford County, Pennsylvania - south
Chemung County - west
Tompkins County - northwest