Indiana County was created on March 30, 1803, from parts of Westmoreland and Lycoming Counties and probably named for the Territory of Indiana. It was attached to Westmoreland County until 1806. Indiana, the county seat, was laid out in 1805 and incorporated as a borough on March 11, 1816.

Indians and traders were the initial visitors to Indiana County, followed by the Native Americans who traveled along War and Game paths such as the North-South Catabwa Path and the traders traversing the East-West Kittanning Trail. It was along the Kittanning Trail in Indiana County that Colonel John Armstrong led his expedition of 300 frontiersmen to overwhelm the Indians at Kittanning after first encamping at Cherry Tree and stopping at the Indiana Spring which today can be visited on the IUP Campus.

Peace with the Native Americans was ultimately reached largely through the Purchase of 1776 in which the Great Nations ceded the land south of "Purchase Line" leaving nearly all of the county free for settlement.

From that frontier wilderness in the eighteenth century, Indiana County had its initial growth as an agricultural county and prospered as a power center in the modern era. Indiana County thrives with an economic base combining education, agriculture, energy production and commerce into an outstanding quality of life for its 90,000 residents.

It is uniquely both the Christmas Tree Capital of the World and a major national center for energy production. More than 14,000 students are studying a variety of disciplines at the Indiana University of Pennsylvania while in Smicksburg the Amish continue their traditional lifestyle. The County remains a recreation mecca with a major state park, five county parks and eight state gamelands abounding in wildlife.