Mills County was created and organized in 1887 from parts of Brown, Comanche, Hamilton and Lampasas counties and named in honor of John T. Mills, a district judge during the days of the Republic of Texas.

Mills County is traditionally founded in production agriculture with total cash receipts from agricultural enterprises ranging from $27-29 million. The primary agricultural enterprises ranked in order of importance include: beef cattle (39%), forage crops (19%), sheep and goats (14%), pecans (7%), small grains (5%), and recreation (<1%).