The mountains of southeastern Kentucky were one of the last regions in the state to be settled. The first known exploration of Kentucky was by Dr. Thomas H. Walker in the 1750's. It is probable that the following decade there were many small parties of hunters exploring the central region of the state.

Daniel Boone made his first trip into Kentucky with a party of fellow hunters in the 1760's and moved his family to what was to become Boonesboro in 1773. He is credited with the discovery of the Cumberland Gap by many although it is believed Dr. Walker was actually the first white man through the gap. Boone certainly earned the credit for having made the gap known and used by thousands of later settlers. Both Harrodsburg and Boonesboro were formed about this time and numerous small settlements sprang up throughout the Bluegrass region by 1780.

Originally claimed by the colony of Virginia as part of its Augusta County, it became Kentucky County, Va., in 1776. Throughout the following decade there were frequent battles and skirmishes with the Indians and their allies the British.

In 1780, Kentucky County was split into three counties, Lincoln, Jefferson and Fayette. Ten years later, these three counties were divided into nine, adding Mason, Bourbon, Woodford, Madison, Mercer and Nelson Counties. Two years later, on June 1, 1792, Kentucky is admitted as a state to the Union.

At that time, settlers were only just beginning to spread into the Kentucky mountains.. Earlier, there had been plenty of land available in the fertile, level central section, but as the region attracted more and more people, there was less land to which for them to settle.

In 1799, a portion of Lincoln County was split off into Knox County. This new county, still largely unsettled in its eastern mountain section, included the Cumberland Gap, still one of the major entry points for westward-moving settlers from Virginia and North Carolina. It was named for Colonel James Knox.

Knox had first explored Kentucky in 1770, leading a party of nine other "Long hunters," so-called because of the long periods of time they would spend on a hunt. The Knox party and that of Daniel Boone each spent about two years hunting throughout the region. Much of that time they were both in the region, although they never met. Knox is listed as one of the 1788 members of the Virginia legislature, representing Lincoln County.

In 1818, the Kentucky Legislature passed an act creating Harlan County out of a portion of Knox County. It was named for Major Silas Harlan. In August of 1782, Harlan was among the 60 men killed by the Indians at the battle of Blue Lick.

The new county's border began at the Cumberland Gap including the eastern half of present-day Bell County, the southern third of Leslie County and the southwestern section of Letcher County. Harlan County remained this size until 1842 when a portion of the northeastern section of the county was joined with a part of Perry County to form the new county of Letcher, named for then Governor, Robert P. Letcher.

It was not until 25 years later, after the Civil War that Harlan County was reduced further in size. At this time the western part of the county was removed and with a portion of Knox County formed into the new county of Joshua Bell, the name soon shortened to just Bell. It was named for Joshua Fry Bell, a great-grandson of the early explorer Dr. Thomas Walker and a representative to the United States Congress from 1845 to 1847.

Only 11 years later, in 1878, Harlan's boundaries were reduced for the last time when the northern part of the county was added to the western part of Perry County and the eastern part of Clay County to become the new county of Leslie. One of the last counties to be formed in the state, it was named for Preston H. Leslie who was governor of Kentucky from 1871 to 1875.