Hill County was named for Dr. George Washington Hill, who had served as President Sam Houston's secretary of war and who had been elected to the state legislature from Navarro County in 1851.
In an effort to stimulate land speculation, army doctor Josephus Murray Steiner and Elijah Sterling Clack Robertson, son of Sterling C. Robertson, devised a plan to divide Navarro County. A petition was circulated on September 19, 1852, to carve a new county from Navarro County. Things moved quickly as Governor Peter Hansbrough Bell called a special session of the legislature
to deal with frontier problems; a bill to divide Navarro County
was signed on February 7, 1853.
A special session of the commissioners' court was called on August 23, 1853, to select the county seat. Thomas Steiner, John Caruthers, and Jonathan Newby offered to donate 260 acres as the county seat; their offer was accepted. Another special session was called on September 24 to survey the town of Hillsborough; town lots went on sale November 1.
C. N. Brooks, the county clerk and justice of the peace, built the first courthouse, which was twelve feet square and consisted of elm poles around a dirt floor. A second courthouse was built in 1854, at a cost of $200. In the same year, post office rules changed, and the town's name became spelled as Hillsboro.
Cities and towns