Sullivan County was created on March 15, 1847 from part of Lycoming County. It was named after Senator Charles C. Sullivan, Butler County, who took an active part in procuring passage of the bill.  Laporte, the county seat, was laid out in 1850 and incorporated as a borough in 1853.  Laporte was named for John LaPorte, Surveyor General of Pennsylvania from 1845-1851.

Prior to the formation of Sullivan County, the area had been included in the New Purchase from the Indians in 1768.  But Connecticut settlers, who had been ousted from the Wyoming Valley, entered and then had to be run off by Pennsylvania agents. Pennsylvania settlers were then, in turn, pushed out by the Indian and Tory attacks of 1778-1780.

The Genesee Road from New York opened up the area, and in 1794 Aristide Dupetit Thouars, a French refugee, was one of the first settlers of the area which later bore a derivation of his name - the town of Dushore.

A woolen industry was productive from 1802 until about 1860 in Forksville. Lumber and related leather tanning industries were most productive throughout the county from 1850 to 1900.  Coal was discovered and mined in several areas of the county. In the early 1800's, Lewis Lake (Eagles Mere) was noted for its glass making industry. Today, tourism is Sullivan County's major industry, followed by lumbering and agriculture.

Under Pennsylvania law, there are four types of incorporated municipalities:

• cities,

• boroughs,

• townships, and

• towns.

The following townships and boroughs are located within Sullivan County's borders:

• Cherry Township

• Dushore Borough

• Colley Township

• Davidson Township

• Eagles Mere Borough

• ElklandTownship

• Forks Township

• Forksville Borough

• Fox Township

• Hillsgrove Township

• Laporte Township

• Laporte Borough

• Shrewsbury Township