Indigenous peoples were the first inhabitants of the area. Later known tribes in the area included
Tonkawa,
Lipan Apache, and
Comanche. The Aguayo expedition is said to have passed through the county in 1721. In 1756, a
presidio was established by Don Pedro de Terreros with the assistance of elements of the Spanish Army, at the confluence of Lucy Creek and Arroya Cavalto. The effort was abandoned not long after, but the site remained as a base of operations by Thomas Isaac Cox, a member of Terreros' original expedition, for the purpose of obtaining hundreds of Texas mustangs for use by the Continental Army during the American Revolutionary War. In 1853, Moses Hughes and his invalid wife, Hannah (Berry), became the first permanent settlers, seeking to take advantage of the medicinal springs. John Patterson was the first man to cultivate land in the county, in 1854. In 1855, Elizabeth and George W. Scott laid out the town of Burleson, named for her father. The town was renamed
Lampasas, when it became the county seat; Indian raids increased in 1861, as able-bodied men were off fighting in the war. Henry A. Chadwick and son Milam built a sawmill, flour mill, and cotton gin in 1874. In 1875, the
Farmers' Alliance was formed in Lampasas in reaction against the cattle rustling and illegal land dealings prevalent in the county. A gunfight occurred at the Lampasas Saloon in 1877. In 1882, the Gulf, Colorado and Santa Fe Railway extended its line west from Belton to Lampasas. The Texas Power and Light Company arrived in Lampasas County in the 1920s, and in 1934 the
Lower Colorado River Authority brought electricity to the county. Lone Star Gas established services in the county in 1949. During
World War II in 1942,
Fort Hood opened as a military training base. Hancock Park in Lampasas was temporarily turned over to the troops as a recreational area. In July of 2025, a major flood of the
Lampasas River happened due to heavy rain upriver. The river level went from around 10 feet to a "major flood stage" of 33 feet. Numerous businesses were damaged, including Hancock Park and Thirsty Penguin. The Boy Scouts ferry system that was set up in that park was completely swept away. Evacuations in RV parks in the city of
Kempner were mandatory. ==Geography==