Created on March 26, 1804 from part of Lycoming County and named for President Thomas Jefferson. It was attached to Westmoreland County until 1806 and then to Indiana County until 1830, when it was formally organized. Brookvillle, the county seat, was laid out in 1830 and incorporated as a borough on April 9, 1834. It is said to have been named for the numerous brooks and in the vicinity.

     Punxsutawney was a Delaware Indian village on the Great Shamokin Path. Pennsylvania acquired the region at the Treaty of Fort Stanwix, or “Last Purchase,” in 1784. Lumber, marketed via conveniently southward flowing streams, was the first industry and also led to boat building. Large-scale coal mining began after the Civil War, assisted by a Pennsylvania Railroad trunk line (opened in 1873), English capital investors, the Pennsylvania Geological Survey, and good advertising. Mining fell off in the mid-1920s due both to labor discontent and the falling coal market, but Jefferson is still the state’s ninth most productive bituminous county. Natural gas made possible a glass manufacturing industry beginning in 1897. Although farms cover one-fifth of the county, agricultural cash receipts are not high. Manufacture of building structural elements and mining-related items is important in today’s economy. The value added from manufactures increased 56 percent between 1987 and 1992. Punxsutawney’s Groundhog Day is one of the nation’s favorite myths, and the Cook Forest State Park (shared with Clarion County) is the only significant preserved stand of primeval hemlock and white pine trees in the state.